EasyJet said passenger traffic rose 6.2 per cent to 5.25m in October, but this growth is lower than the seven per cent increase seen over the past year.
The carrier’s load factor, a measure of how well it fills planes, fell 0.4 percentage points to 88.4 per cent.
EasyJet has opened a string of new routes over the last year, and hopes to begin flights to Moscow next year.
Aer Lingus, which reports third quarter results today, said its October traffic rose 0.9 per cent on a year ago to hit 962,000.
Its growing long haul services saw a 10.3 per cent jump in traffic to 86,000. Passenger numbers on regional flights also took off, rising 34 per cent on last year to 89,000.
These gains were offset by a 2.7 per cent slide in short haul traffic to 787,000 passengers.
Year to date, Aer Lingus has enjoyed a 3.7 per cent increase in traffic to 9.16m.
The Irish airline is trying to fend off takeover interest from larger rival Ryanair, which said on Monday it is willing to offer regulators more concessions in order to smooth the path of the €694m (£556m) deal.