How much time should you allow for a shared shuttle transfer to Istanbul Airport?

In one recent case, the shared shuttle left immediately after boarding and took about 1 hour 40 minutes, including a 15-minute shop stop. However, the driver dropped passengers on the highway rather than entering the hotel grounds.

Cutting it close is risky: one traveler left 3.5 hours before the flight, hit a long queue at the terminal entrance, spent about 30 minutes getting from the drop-off point to the terminal, and check-in had already started by the time they arrived.

A shared shuttle can be delayed by the driver: after the airport there was a supposed 'toilet break' that turned out to be a 30-minute stop at a souvenir shop, and after each hotel drop-off the driver spent about 10 minutes on his phone. If you need to arrive within roughly 2 hours, book a private/individual transfer instead.

Boarding a shared airport shuttle feels like boarding a shared minibus: staff check your name off a list (a 5-7 minute wait), then the group takes an elevator down to the parking area where passengers are split up among several minivans.