I noticed on an American Airline flight a gap of about 4 inches between the floor of the bridge and the airplane. Wide enough that if the passenger is not paying attention to the floor the foot may slip in between or at least get stuck. The flight attendant said there's always a gap. I've seen a gap but not that wide. Is there a maximum acceptable gap?
In general, there is a gap between the jet bridge (also called Passenger Boarding Bridges or PBB) and the aircraft. This is due to various reasons like,
- To prevent damage to the fuselage
- The jet bridge may not fit all the aircraft similarly as their fuselage dimensions are different.
According to FAA Advisory Circular 150/5220-21C,
The PBB should be equipped with sensors to safely prevent dangerous contact with the aircraft
The jet bridges at most airports are designed for larger passenger aircraft that are higher off the ground. When a small aircraft utilizes these jet bridges they must use a "ramp" to bridge the gap between the jet bridge and the aircraft.
According to the same Circular,
The maximum horizontal gap allowable along the path to the aircraft can be no greater than 1.25 in (32 mm)
So, I guess that a 4 inch gap is not allowed.