A perfect airlock will mess with liaisons and other visitors who need to path to a meeting. You can remedy this either by making your meeting-dwarf enough of a badass to stay in the airlock and swat aside any unwelcome visitors, or by using hatches in place of the retracting bridge. This will create a 100-tick window in which both sides of the airlock are open, so you should either burrow your dwarves or plan the layout so that nobody has any reason to be within 100 ticks of the hatches*.
This will make the liaison run for the fortress until they bash their head against the now-closed hatch, at which point they will be in the airlock.
*Assuming that speed calculatations haven't changed since 40d and the wiki is correct, and also that my maths is correct, Displayed Speed = 1,000,000 / (Raw Speed+100) and so Raw Speed = (1,000,000/Raw Speed) - 100. With the default values, the maximum Agility a normal dwarf can reach is 3000, for a raw speed of 233.3... (for comparison, ravens have a raw speed of 400). A dwarf moving at this maximum waits two ticks to move, with a 33.3... % chance of waiting a further tick to move. In 100 ticks, it will cover anywhere from 33 to 50 tiles, the average being 44 tiles.
Edit: I think that's right now, though that average seems on the high side.