Closing Airport Road affects these routes: Brampton Transit — 101 Airport Express (early-morning only); GO Transit — 34 Brampton Local; Mississauga Transit — 7 Airport; TTC — 58 Malton.

Routings in the airport area are complex. Some TTC buses start and end their trips at the airport while others continue through the airport to continue their trips.

This is the likely route for buses through the area when Airport Road is closed:

From 11 p.m. until 5 a.m. Monday, March 30 until Thursday, April 2, (early Tuesday, March 31 until early Friday April 3), southeastbound buses operate along their regular route to Airport Road and American Drive, then detour:

northward along American;
eastward along Viscount and Campus Roads; and then
southward along Bresler Drive to Airport Road / Jetliner Drive.

Buses then continue southward along Jetliner Drive, loop through Toronto Pearson International Airport and return to Jetliner Drive at Airport Road / Bresler Drive, resuming their regular route.

From 11 p.m. until 5 a.m. Monday, March 30 until Thursday, April 2, northwestbound buses operate along their regular route to Airport Road and Jetliner Road / Bresler Drive, then detour:

southward along Jetliner Drive;
loop through Toronto Pearson International Airport;
returning to Jetliner Drive and Airport Road / Bresler Drive, then detouring

northward along Bresler Drive;
westward along Campus and Viscount Roads; and then
southward along American Drive to Airport Road,
resuming their regular route.

You can see a map of the Mississauga Transit detour — which, unfortunately, does not indicate that the buses also travel through the airport — here. (.pdf)

The TTC has announced that, starting at 6 a.m. on Tuesday, March 31, it is relocating its stops at Terminal 3 for three months.