An airport towing tug emitted thick smoke that was sucked into the cabin by the plane’s air-conditioning system. Although the pilot repeatedly announced to passengers that the smoke was coming from outside and that there was no danger, those on board apparently left their seats and rushed the doors.
To the extent that, up to this point, everything that every employee had said to the passengers, from reservation through ticket purchase, check-in, security, boarding, had turned out to have been 100% true, the passengers should have believed the pilots.
Pilots who want their passengers to believe them in emergency situations should encourage their airline to develop a reputation for scrupulous honesty in all interactions with passengers at all levels of the organization.