The second of two 12-hour strikes has begun at Glasgow and Aberdeen airports.
The move follows stalled talks between the AGS Airports group and the Unite union over pay and pensions.
Unite members at the two airports have walked out until 16:00 on Monday. The first strike . Strikers include security staff, fire and operations teams - but not check-in or baggage handlers.
AGS Airports, which owns the airports, said it was "business as usual".
AGS said in a statement: "We are very pleased that the contingency plans we put in place ensured it was a case of business as usual at both airports.
"We have kept our airports open ensuring thousands of passengers and hundreds of flights have been able to travel and operate safely."
During Friday's strike, passengers experienced security and flight delays.
The union claims on 24 May, as it attempted to close a defined benefit pension scheme.
This, they say, broke an Acas Agreement made in 2016 to keep the scheme open to existing members.