A pair of air traffic controllers have been fired and officials are probing a Monday landing incident involving First Lady Michelle Obama, as weeks of embarrassing sleeping incidents and procedural gaffes have prompted a top-to-bottom review of federal air traffic controller training.

We have the safest aviation system here in the United States, anywhere in the world but we have to do better, said Transportation Secretary Ray Lahood on the PBS' News Hour on Wednesday. We are doing better. We're conducting investigations and I'm prepared to announce tonight that we have fired two controllers after completing two investigations. We're also changing procedures having to do with the vice president, the first lady's plane, when they're flying in and out of Washington air space.

The firings involve two separate incidents separate from an incident at joint Base Andrews in Maryland when an FAA controller mistakenly allowed the first lady's plane to get within 3 miles of a military transport jet. Her plane aborted a landing attempt and had to circle until it could land safely. LaHood said at no time was the First Lady in danger.

The first firing involved a March 27 incident in Miami, Florida when a controller ordered a 737 Southwest jet to check on a smaller plane out of radio contact. Placing the passenger plane in close proximity to the other endangered the safety of all involved.

Completely violates procedures. You can't guide a big plane to look over a small plane. That's not the way that's done, LaHood said.

In a second incident in Tennessee, LaHood said a controller in Tennessee actually made a bed in the control tower, brought a pillow, brought blankets. He's been fired. We're not going to going to sit by and let that kind of behavior take place in the control towers.

The National Transportation Safety Board - which usually investigates aircraft accidents - on Wednesday said it is investigating Monday's incident involving the First Lady's plane. Lahood said Wednesday that from now on, supervisors will be required to handle the flights with the First Lady and Vice President Joe Biden. Currently, supervisors  are required to handle President Barack Obama's flights.