Originally Posted by
pittpanther
This. By checking in online, you limit your risk to only the duration of the TSA line. How long that might be depends on your airport.
I know every country, even every airport is different and the OP doesn't mention where he's travelling from, but there are a few other potential delays.
Departure fee payment.
Bag drop queues.
ID and boarding card check.
Security (non TSA in most of the world).
Distance from security to gates.