# Is prior clearance into Class B airspace revokable?

I was piloting outside of Class B airspace in an area well known for being difficult from which to contact ATC via radio because of mountainous terrain. When I did get cleared into Class B, I was only about a mile outside of Class B airspace. Immediately, another controller took over (different gender / same frequency), revoked the clearance, and said to stay clear of Class B and scolded me for only being one mile outside of Class B. (I complied with that request, never entering Class B – so there was no violation.)

Question: Can you legally be “uncleared” into Class B after receiving a clearance into Class B? Could you speculate on what may have happened?

• Unless you are in an emergency, you are required to comply with all ATC instructions, so yes, a clearance can be revoked. Just like a landing clearance or crossing clearance. The controller shouldn't have scolded you though, you were clear of the airspace, unless you were coming in at a fast rate. Ideally you'd like to get clearance quite a bit before that. I like to contact Class C at least 20 miles out, and for Class B I'd get flight following if possible as I left my origin. Aug 22, 2016 at 3:03
• Sure, a clearance can be changed or even revoked. It happens all the time. The traffic situation may change, equipment could fail, an emergency could appear, etc. Air traffic control is extremely dynamic - the work of the controller can change 100% in as little as 5 minutes. Aug 22, 2016 at 4:22
• I'd listen to the conversation on liveatc.net and make sure that it really did happen as you recall. If it did, I'd file an ASRS report: as you described it, it seems that the handover from one controller to another wasn't done well. If the second controller "scolded" you then s/he was presumably unaware of the previous clearance issued, and that shouldn't be the case. Aug 22, 2016 at 13:33
• @Pondlife It doesn't sound like a frequency change to me. More likely, a supervisor cut in after the other controller already gave the clearance because they weren't comfortable with the potential situation. I hear this happen every once in a while. Aug 24, 2016 at 1:38
• @Lnafziger That's an interesting idea, I didn't think of that. But then why would the supervisor scold the pilot if the mistake was on the ATC side? I actually understood it was a controller change, not a frequency change. Aug 24, 2016 at 13:09

Every clearance can be cancelled or revoked, irrespective of the type of clearance.

My speculation on what happened is: The first controller was in training and the second controller was their trainer. The trainee cleared you into the Class B but the trainer though that was a bad idea (perhaps there was traffic nearby they couldn't have kept you away from, or they wanted to teach you a lesson about calling too late, or they thought their trainee was too busy to provide VFR services, or they woke up on the wrong side of the bed that morning) and came on frequency to contradict the trainee's clearance.

When controllers are first hired, and any time they transfer facilities, they have to complete on-the-job training. This is because:

1. Learning how to control simulated traffic in the schoolhouse is not good enough to let a new controller talk to actual planes with actual people in them making actual crazy requests they never had to deal with in the simulator.
2. Airspace and procedures are different everywhere. Even if you were the best of the best at your last facility, you don't know all the nuances of the new facility.
3. Different facilities have different controlling techniques and requirements. It's very possible for someone to transfer from a tower-only flight-school-heavy facility to a radar approach control working commercial traffic into a Class B or even to an enroute center.

That's why you'll sometimes hear a second voice come on frequency and tell you to disregard what the first controller just said. It won't be a supervisor, it'll be a certified controller who is conducting training.