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What You Need To Know About Class A Airspace

Flying into Class A airspace is more than just filing an IFR flight plan. What happens if you're in the flight levels under visual conditions and experience a radio failure? Do you follow the standard route and altitude procedures described in FAR 91.185, or do you deviate and land as soon as practical?

Here's what to do...



You'll be required to fly under instrument flight rules (IFR) in Class A airspace, according to FAR 91.135. That means you'll need a clearance before operating inside Class A. This doesn't mean you have to be "cleared into the Class A;" just having an IFR clearance with an altitude into the Class A is enough.

You'll also need to maintain two way radio communications with ATC and follow FAR 91.215 when it comes to transponders with altitude reporting capabilities. After January 1st, 2020, any aircraft operating in Class A airspace will be required to follow FAR 91.225, which details requirements for the installation and use of ADS-B and TIS-B equipment.


Aerobatics are prohibited in Class A airspace. Without prior permission from ATC, ultralight vehicles and parachute jumps are also prohibited within Class A airspace. One nice benefit of flying through Class A? There are no weather minimums to worry about since you're under IFR!


It's Not Marked

Unlike other forms of airspace, Class A is not marked on VFR sectionals or IFR enroute charts. Class A extends from 18,000 feet MSL to Flight Level 600 (FL600). So, in an alternate universe, if you manage to get your Cessna Skyhawk sputtering up above FL600, you technically could cancel your IFR clearance and fly under visual flight rules.


But What Exactly Is A "Flight Level?"

A flight level is an altitude at standard pressure. All aircraft flying above 18,000 feet MSL are required to set their altimeters to 29.92 inches on their altimeters. This means that all aircraft flying in the flight levels will have the same altimeter setting, no matter what, so that aircraft can be separated and clear of each other. FL180 on a standard day (pressure setting of 29.92 inches) would equal 18,000 feet MSL. At a different atmospheric pressure, actual altitude above sea level would vary.

Swayne Martin

Aircraft flying in the flight levels fly at thousand-foot levels, ie: FL190, FL220, FL430, etc. And when aircraft have the right equipment, Reduced Vertical Separation Minimums in Class A allow aircraft to fly just 1,000 feet above and below each other.

You'll usually find jets and turboprops flying in Class A airspace, but you also might find some turbocharged and turbonormalized piston aircraft, like the Cirrus SR22T we fly out of Boulder, Colorado. Check out some of our adventures in the flight levels here.


What Happens If Your Radio Or Transponder Fails?

It's rare to lose your radios or transponder without other serious electrical problems. But if you do have an individual radio or transponder failure, follow the checklists for your airplane and try to problem-solve.


FAR 91.185 prescribes the procedures for handling a radio failure in IMC.

If you're flying in IMC, follow the route and altitude specified under 91.185. With all of these rules in mind, what happens if you break out of the clouds into VMC? If you encounter VFR conditions during a radio failure, you should continue the flight under VFR and land as soon as practical. This procedure is the same whether you're in Class A airspace or not. ATC would rather aircraft divert safely under visual conditions, if possible, than remain the IFR system without radios for hundreds of miles.

Advanced aircraft have multiple backup sources for communication if radio problems are experienced. But if you're flying something older, technology at your disposal may be limited.

Smithsonian National Air and Space Museum

Planning a descent from the flight levels all the way to an airport below requires good weather conditions, since you'll need to maintain VFR the whole way. Keep in mind, however, that the closest airport might not be your best option. If your radio is broken, you're going to need to get it fixed. And picking an airport with maintenance services (if possible) is better than landing at an airport with nothing but a runway and a self-serve gas pump.


Total Electrical Loss

If you lose the operation of a radio or transponder, you're normally dealing with serious electrical problems. Often times, the radios and transponder are some of the first items to go offline because of how much electrical current they draw. If you begin to lose all electrical power in Class A airspace, in either visual or instrument conditions, you should declare an emergency and get to visual conditions as soon as possible. The worst case scenario is being stuck in instrument conditions with a dying electrical system.

ATC will usually assume you're experiencing an emergency if they lose both radio and transponder communication with you. But if these problems occur in high-risk security areas like Washington DC, it's possible that you might be intercepted by the military to confirm that you're having a legitimate emergency.

What Exceptions Are There?

Under FAR 91.135, deviations from the requirements of Class A can be issued by the ATC facility governing that section of airspace. To request a deviation from the regulatory requirements of Class A airspace, you have to submit, in writing, a request at least 4 days before the proposed operation to the relevant ATC facility.

Some operations where you'll commonly find deviations include high altitude skydiving and aerial survey work. ATC can issue blocks of airspace by request, technically within the boundaries of Class A airspace for these unusual exceptions. Just make sure you stick to those assigned altitudes!

Max Lesziak

Easy enough, right? Even though you may be flying miles above the ground, little changes in terms of IFR regulations for Class A airspace. If you're flying in the flight levels, you'll stay above much of the bad weather and can find some seriously strong tailwinds. But you'll need to know the regulations, set your altimeter correctly, and pay extra attention to altitude restrictions.

What aircraft have you flown in Class A airspace? Tell us about it in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and an Embraer 145 First Officer for a regional airline. He graduated as an aviation major from the University of North Dakota in 2018, holds a PIC Type Rating for Cessna Citation Jets (CE-525), and is a former pilot for Mokulele Airlines. He's the author of articles, quizzes and lists on Boldmethod every week. You can reach Swayne at, and follow his flying adventures on his YouTube Channel.

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