Wizz Air, the London-listed budget airline, carried 7.62 million passengers in October, up 19.8% on the same month last year.
Capacity grew faster, rising 22.1% to 8.36 million seats.
As a result, the load factor, which measures the proportion of seats filled, slipped 1.7 percentage points to 91.2%.
Over the last 12 months, Wizz Air carried 80.6 million passengers, a rise of 19.6%.
Spain is central to the airline's latest push.
Wizz Air opens new bases in Madrid and Valencia this week, with three aircraft based there serving 16 routes.
It also launched flights from London Luton to Málaga, Granada and Asturias in October, taking its Spanish destinations from Luton to ten.
Separately, the airline is adding two daily return flights from Madrid to both Málaga and Seville between 6 November and 13 December.
The temporary services follow the suspension of high-speed rail links between Madrid and Andalusia, and fares are capped at €99.99.
In Poland, Wizz Air launched ten new routes from five airports to Egypt for the winter season.
The airline also signed a distribution deal with Amadeus, the travel technology company, in October.
The agreement makes Wizz Air fares and extras available to travel agents, online travel agencies, tour operators and corporate travel managers in selected markets.
Carbon dioxide emissions rose 14.5% to 614,604 tonnes in October.
Emissions per passenger-kilometre were broadly flat on the month at 49.3 grams, but improved 2.5% over the rolling 12 months.
The figures exclude any benefit from sustainable aviation fuel.
Wizz Air, which operates 275 Airbus A320 and A321 aircraft, will publish results for the six months to 30 September on 12 November.
