It’s been reported that the passengers on Flight 93 had boarded the plane via the boarding ramp/jetway at Newark Airport:
Flight 93: Forty lives, one destiny
The Flight 93 passengers had walked down the concourse of Terminal A, where they breezed past the security gate, then walked the 100 yards to a long circular hallway from which the boarding ramps jutted out like spokes.
At Gate 17, they strode another 70 feet down the jetway, made a left turn, and were inside the Boeing 757. – post-gazette.com (10/28/01)