Budget carriers Ryanair and Wizz Air announced rising passenger numbers for December, with the latter growing traffic by 20 per cent.
The Hungarian airline said rolling annual traffic to December was up by 21 per cent to nearly 31m.
Wizz Air said passenger numbers for last month rose by 19.8 per cent on December 2016, with load factor - assessing how efficiently it fills its planes - also on the rise. That edged up 0.2 percentage points to 87.5 per cent.
Last month, the airline announced it had signed an agreement for the purchase of 146 Airbus A320neo aircraft valued at over $17bn (£12.6bn) to deliver its fleet replacement and expansion plans.
It also announced three new routes from London Luton Airport as it bolsters its presence in the capital, having opened a base at Luton last June.
Ryanair meanwhile, reported traffic rising by three per cent on December 2016 to 9.3m passengers, with load factor rising one percentage point to 95 per cent. Rolling annual traffic to December grew 10 per cent to 129m customers.
Analysts at Dublin-based Goodbody noted growth had "slowed sharply" into a period impacted by the raft of cancellations Ryanair faced relating to rostering issues.
However, they added this had been expected, and leaves the growth required in the fourth quarter to hit their full-year target at 4.4 per cent. Analysts said this was an "easily achievable" target, with some of 2018's Easter trade falling into that period.
Both airlines are among those in the industry to be making Brexit contingency plans, after Ryanair confirmed yesterday that it had applied for a UK licence to protect its operations in the event of a hard Brexit.