[{"data":1,"prerenderedAt":314},["ShallowReactive",2],{"learn-\u002Flearn\u002Fminimum-safe-altitudes-msa-mora-mea-moca":3,"learn-nav-\u002Flearn\u002Fminimum-safe-altitudes-msa-mora-mea-moca":281},{"id":4,"title":5,"body":6,"date":219,"description":220,"draft":221,"extension":222,"faqs":223,"howTo":233,"keyTakeaways":234,"meta":239,"navigation":240,"path":241,"quiz":242,"seo":266,"series":267,"seriesOrder":268,"sources":269,"stem":278,"topic":279,"__hash__":280},"learn\u002Flearn\u002Fminimum-safe-altitudes-msa-mora-mea-moca.md","Minimum safe altitudes: MSA, MORA, MEA, MOCA and MEF",{"type":7,"value":8,"toc":210},"minimark",[9,13,19,24,47,103,116,120,142,146,162,179,183,203,207],[10,11,12],"p",{},"Terrain does not move, and the altitudes that keep you above it are some of the most important numbers on a chart. The trouble is that there are several of them, with similar-looking abbreviations, and they do not all promise the same thing. Knowing exactly what each one guarantees, and which one is not a safe altitude at all, is basic terrain awareness.",[14,15,16],"blockquote",{},[10,17,18],{},"This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.",[20,21,23],"h2",{"id":22},"the-altitudes-that-guarantee-clearance","The altitudes that guarantee clearance",[10,25,26,27,34,35,40,41,46],{},"These four are designed to keep you safely above terrain and obstacles, with the clearance already built in. The ",[28,29,33],"a",{"href":30,"rel":31},"https:\u002F\u002Fwww.faa.gov\u002Fregulations_policies\u002Fhandbooks_manuals\u002Faviation\u002Finstrument_procedures_handbook",[32],"nofollow","FAA Instrument Procedures Handbook",", the ",[28,36,39],{"href":37,"rel":38},"https:\u002F\u002Fwww.faa.gov\u002Fair_traffic\u002Fpublications\u002Fatpubs\u002Faim_html\u002Fchap5_section_3.html",[32],"FAA AIM"," and the ",[28,42,45],{"href":43,"rel":44},"https:\u002F\u002Fww2.jeppesen.com\u002Fnavigation-solutions\u002Fairway-manual\u002F",[32],"Jeppesen Airway Manual"," define them:",[48,49,50,66,79,93],"ul",{},[51,52,53,57,58,61,62,65],"li",{},[54,55,56],"strong",{},"MSA, minimum sector altitude",": shown on approach charts, it gives at least ",[54,59,60],{},"1000 feet"," of obstacle clearance within ",[54,63,64],{},"25 nautical miles"," of a reference point, usually split into sectors. It is an emergency terrain-awareness figure, not a routine approach altitude.",[51,67,68,71,72,74,75,78],{},[54,69,70],{},"MORA, minimum off-route altitude"," (a Jeppesen figure): clears terrain and obstacles within a defined band either side of a route, or in a grid square, by ",[54,73,60],{}," where the highest point is up to 5000 feet, and by ",[54,76,77],{},"2000 feet"," where it is higher.",[51,80,81,84,85,88,89,92],{},[54,82,83],{},"MEA, minimum en-route altitude",": along an airway, it assures ",[54,86,87],{},"both"," obstacle clearance ",[54,90,91],{},"and"," an acceptable navigation signal for the whole segment.",[51,94,95,98,99,102],{},[54,96,97],{},"MOCA, minimum obstruction clearance altitude",": assures the same obstacle clearance along the airway, but only guarantees the navigation signal ",[54,100,101],{},"within 22 nautical miles"," of the navigation aid.",[10,104,105,106,111,112,115],{},"The general clearance values behind these, per ",[28,107,110],{"href":108,"rel":109},"https:\u002F\u002Fstore.icao.int\u002Fen\u002Fprocedures-for-air-navigation-services-pans-aircraft-operations-volume-i-flight-procedures-doc-8168",[32],"ICAO Doc 8168"," and the FAA, are ",[54,113,114],{},"1000 feet in non-mountainous areas and 2000 feet in designated mountainous areas",".",[20,117,119],{"id":118},"the-one-that-is-not-a-safe-altitude","The one that is not a safe altitude",[10,121,122,123,126,127,133,134,137,138,141],{},"The ",[54,124,125],{},"MEF, Maximum Elevation Figure",", is different in kind, and the difference catches people out. Printed in each latitude and longitude quadrangle on a ",[28,128,132],{"href":129,"className":130},"\u002Flearn\u002Fglossary#gt-vfr",[131],"glossary-link","VFR"," chart, the MEF is the elevation of the ",[54,135,136],{},"highest terrain or obstacle in that box, rounded up",". It has ",[54,139,140],{},"no clearance margin built in",". It tells you the highest thing in the square and nothing more; the safe cruising altitude is whatever you choose to add above it.",[20,143,145],{"id":144},"a-worked-example","A worked example",[10,147,148,149,152,153,156,157,161],{},"Planning a VFR leg across a chart, you read an ",[54,150,151],{},"MEF of 5400 feet"," in the quadrangle your track crosses. That is the top of the highest obstacle in that box with no margin. To set a cruising altitude you add your own clearance, say 1500 to 2000 feet for comfort over rising ground, giving roughly ",[54,154,155],{},"7000 to 7400 feet",", before you then round to a ",[28,158,160],{"href":159},"\u002Flearn\u002Fvfr-weather-minima-and-cruising-levels","VFR cruising level"," appropriate to your direction of flight.",[10,163,164,165,170,171,174,175,178],{},"Contrast the ",[28,166,169],{"href":167,"className":168},"\u002Flearn\u002Fglossary#gt-ifr",[131],"IFR"," picture on the same route: an airway segment shows an ",[54,172,173],{},"MEA of 7000 feet"," and a ",[54,176,177],{},"MOCA of 5500 feet",". You may, in the right circumstances, descend to the MOCA and still be clear of obstacles, but beyond 22 nautical miles from the navigation aid you are no longer assured of the signal, so the MEA is the altitude that keeps both your terrain clearance and your navigation honest along the whole segment.",[20,180,182],{"id":181},"common-pitfalls","Common pitfalls",[48,184,185,191,197],{},[51,186,187,190],{},[54,188,189],{},"MEF is the obstacle, not your altitude."," Never fly at the MEF; it is the height of the highest obstacle, with nothing added.",[51,192,193,196],{},[54,194,195],{},"MEA and MOCA differ on signal, not clearance."," Both clear the terrain; only the MEA promises navigation coverage for the full segment.",[51,198,199,202],{},[54,200,201],{},"Mountainous means more margin."," The clearance built into these figures rises to 2000 feet in designated mountainous areas, so the same airway feels very different over high ground.",[20,204,206],{"id":205},"in-pilot-efb","In Pilot EFB",[10,208,209],{},"Pilot EFB is a study and planning companion for terrain-aware route planning, sitting alongside your weather, NOTAMs and flight time in one offline-first place. It does not replace your charts or set your safe altitude for you, so read the published figures from your official source of record and add your own margin. Pilot EFB is not a certified Electronic Flight Bag, so treat it as a study and planning aid and brief from your official source of record.",{"title":211,"searchDepth":212,"depth":212,"links":213},"",2,[214,215,216,217,218],{"id":22,"depth":212,"text":23},{"id":118,"depth":212,"text":119},{"id":144,"depth":212,"text":145},{"id":181,"depth":212,"text":182},{"id":205,"depth":212,"text":206},"2026-06-22","The family of minimum altitudes that keep you clear of terrain and obstacles, what each one guarantees, and the difference between an altitude that also promises navigation signal and a chart figure that only tells you the highest obstacle.",false,"md",[224,227,230],{"q":225,"a":226},"What is the difference between MEA and MOCA?","Both are airway altitudes that guarantee obstacle clearance, but they differ on navigation signal. The minimum en-route altitude (MEA) assures both obstacle clearance and an acceptable navigation signal along the whole airway segment. The minimum obstruction clearance altitude (MOCA) assures the same obstacle clearance but only guarantees the navigation signal within 22 nautical miles of the navigation aid. So MOCA can be lower than MEA, at the cost of reliable navigation coverage further out.",{"q":228,"a":229},"What is a Maximum Elevation Figure on a VFR chart?","The Maximum Elevation Figure (MEF), shown in each latitude and longitude quadrangle on a VFR chart, is the elevation of the highest terrain or obstacle in that box, rounded up. It is not a minimum safe altitude and it includes no clearance margin: it simply tells you the highest thing in the square. You add your own clearance above it to set a safe cruising altitude.",{"q":231,"a":232},"How much obstacle clearance do these minimum altitudes provide?","As a general rule the obstacle clearance built into en-route and off-route minimum altitudes is 1000 feet in non-mountainous areas and 2000 feet in designated mountainous areas. The exact value depends on the authority and the type of altitude, but that 1000-foot and 2000-foot pairing is the standard you will see across the definitions.",null,[235,236,237,238],"MSA, MORA, MEA and MOCA are minimum altitudes that guarantee obstacle clearance; the MEF is only the highest obstacle, not a safe altitude.","MEA guarantees obstacle clearance and navigation signal along the whole segment; MOCA guarantees clearance but signal only within 22 nautical miles of the aid.","Standard obstacle clearance is generally 1000 feet in non-mountainous and 2000 feet in designated mountainous areas.","The MEF on a VFR chart has no margin built in, so add your own clearance above it to choose a cruising altitude.",{},true,"\u002Flearn\u002Fminimum-safe-altitudes-msa-mora-mea-moca",[243,252,260],{"q":244,"options":245,"answer":250,"explanation":251},"What does the minimum obstruction clearance altitude (MOCA) guarantee about navigation signal?",[246,247,248,249],"Signal along the entire airway segment","Signal only within 22 nautical miles of the navigation aid","No signal at all","Signal only above 10,000 feet",1,"MOCA assures obstacle clearance along the airway but only guarantees an acceptable navigation signal within 22 nautical miles of the navigation aid, unlike the MEA which assures signal for the whole segment.",{"q":253,"options":254,"answer":250,"explanation":259},"What does the Maximum Elevation Figure (MEF) on a VFR chart tell you?",[255,256,257,258],"A safe altitude to fly with clearance already added","The elevation of the highest terrain or obstacle in that quadrangle, with no clearance margin","The minimum en-route altitude","The transition altitude","The MEF is the highest terrain or obstacle in the quadrangle, rounded up and with no clearance built in; you add your own margin above it.",{"q":261,"options":262,"answer":212,"explanation":265},"Standard obstacle clearance in designated mountainous areas is:",[263,60,77,264],"500 feet","3000 feet","The standard obstacle clearance is generally 1000 feet in non-mountainous areas and 2000 feet in designated mountainous areas.",{"title":5,"description":220},"plan-a-vfr-cross-country",6,[270,272,274,276],{"label":271,"url":37},"FAA Aeronautical Information Manual (Pilot\u002FController Glossary and en-route procedures)",{"label":273,"url":30},"FAA Instrument Procedures Handbook (FAA-H-8083-16B)",{"label":275,"url":43},"Jeppesen Airway Manual, General section",{"label":277,"url":108},"ICAO Doc 8168: PANS-OPS, Volume I (Flight Procedures)","learn\u002Fminimum-safe-altitudes-msa-mora-mea-moca","Operations","Hbqy24v8EwJnMdtxaSPmHP1YGirasa7xLnHjzZXRH9w",{"related":282,"newer":297,"older":302,"series":306},[283,289,293],{"path":284,"title":285,"description":286,"date":219,"topic":279,"draft":221,"minutes":287,"series":267,"seriesOrder":288},"\u002Flearn\u002Fairspace-speed-limits","The 250-knot speed limit and other airspace speed rules","Why there is a 250-knot speed limit below 10,000 feet, the slower 200-knot limits near and under busy airspace, and how the FAA and EASA wordings line up and differ, with a worked descent that puts the rules in order.",4,7,{"path":290,"title":291,"description":292,"date":219,"topic":279,"draft":221,"minutes":287,"series":233,"seriesOrder":233},"\u002Flearn\u002Freading-an-instrument-approach-chart","Reading an instrument approach chart","How an instrument approach chart is laid out, what the plan view, profile view, minimums box and missed approach each tell you, and how to read one in order so you brief the approach the way you will fly it.",{"path":294,"title":295,"description":296,"date":219,"topic":279,"draft":221,"minutes":287,"series":233,"seriesOrder":233},"\u002Flearn\u002Fsids-and-stars-explained","SIDs and STARs explained","What standard instrument departures and standard terminal arrival routes are, why they exist, and how to read the climb gradients and crossing restrictions that turn a busy terminal area into orderly, repeatable traffic flows.",{"path":298,"title":299,"description":300,"date":219,"topic":301,"draft":221,"minutes":287,"series":233,"seriesOrder":233},"\u002Flearn\u002Fjet-stream-and-clear-air-turbulence","The jet stream and clear-air turbulence","What a jet stream is, where it sits near the tropopause, and why the wind shear around it produces clear-air turbulence that arrives with no cloud to warn you.","Weather",{"path":303,"title":304,"description":305,"date":219,"topic":301,"draft":221,"minutes":287,"series":233,"seriesOrder":233},"\u002Flearn\u002Fmountain-waves-and-rotor","Mountain waves and rotor","How stable air flowing over high ground sets up standing mountain waves and the violent rotor beneath them, the cloud signs that give them away, and why the turbulence and downdraughts deserve respect.",{"slug":267,"title":307,"part":268,"total":288,"prev":308,"next":283},"Plan a VFR cross-country",{"path":309,"title":310,"description":311,"date":312,"topic":279,"draft":221,"minutes":287,"series":267,"seriesOrder":313},"\u002Flearn\u002Fcrosswind-components","Crosswind components","How to resolve a reported wind into its crosswind and headwind components with simple trigonometry, a worked example, the sine rule of thumb, and what a maximum demonstrated crosswind really is.","2026-06-01",5,1782089963538]