CAA data for January to March revealed the airport had the largest percentage of scheduled and chartered flights arriving and departing on time, at 89.4%.
Teesside International took second place and Exeter third spot.
Matthew Hall, Belfast City chief executive, said: “This is great news for those that use the airport for both business and leisure, and stands as a testament to the hard-work and dedication of our entire team.”
Hall said average security processing time was six minutes.
“The phased return of travel has allowed us to recover gradually, which helps control passenger flow and ensures people will have a quick and easy journey through the airport.”
Belfast City offers 20 destinations with eight airlines including British Airways, Eastern Airways, easyJet, Flybe, KLM, and Loganair this summer.
