I fly in and out of ICN about 4-5 times a year. I have had to have an early flight out of ICN each time I have been there. Security can be a nightmare.

My suggestion is go early. I was just there on the 31st of December. The airport was a zoo. The Morning Calm line was just as packed as the economy line, we had 8 windows open versus 6 in economy though. Still it took 30mins to check in. Usually I wait no more than 5 minutes.

Security took 40 minutes. My suggestion is to not use only the C entrance to security. We talked down to the B entrance and that was actually faster. The lines at C were probably in the 60+ minute range.

Also we stayed at the Grand Hyatt nearby so we could be at the airport 3hrs early without waking up at a super early hour and traveling in from Seoul. That was worth it.

Winter traveling is always slow. And yes, no priority lines.