Border Force officials have added March 15 to their planned walk-outs over pay, pensions and job security.
The date of the one-day strike is timed to coincide with the Budget.
The Public and Commercial Services Union (PCS) has already called for a walk-out on February 17-20.
According to aviation data specialist Cirium, 2,125 flights, equating to more than 365,000 passengers, are scheduled to arrive into UK airports on March 15.
Heathrow is set to see the highest number of landings (610), followed by Gatwick (267), Manchester (173), Stansted (168) and Edinburgh (116).
British Airways will be the largest airline by arriving flights (479), followed by EasyJet (408) and Ryanair (265).
