By (Reuters) Berlin – Passengers numbers at Europe's airports grew at the fastest pace in 13 years during 2017, but growth looks set to slow with rising oil prices, airline consolidation and Britain's exit from the European Union all presenting challenges this year. Passenger traffic across Europe rose 8.5 percent in 2017, airport association ACI Europe said on Tuesday, the fastest level since 2004, when traffic was boosted by the accession of 10 new countries to the European Union. "This might be as good as it gets and while we anticipate continued growth in the coming months, it will most certainly come at a slower pace," ACI Europe head Olivier Jankovec said in a statement. ACI Europe said that passenger growth had slowed at the end of last year – to 5 percent in December – due to the insolvencies of carriers Air Berlin and Monarch, plus Ryanair's decision to slow growth in order to deal with pilot rostering issues. Jankovec said while the outlook was good for European economies, rising oil prices putting pressure on airlines and consolidation reducing the number of carriers signalled pressure on airport operators this year. "Couple that with the fast-approaching Brexit deadline on the horizon and it's not hard to see why Europe's airports can expect the temperature to rise, as airlines get even choosier about where they maintain existing capacity or open new routes,” he said. Shares in airport operators Fraport and Groupe ADP rose 62 and 55 percent during 2017 thanks to traffic growth. Of the major airports in Europe, Amsterdam Schiphol grew at the fastest pace, up 7.7 pct, while among smaller airports, Iceland Keflavik grew 28 percent as airlines increasingly use it as a stopover for transatlantic flights and tourism booms. Europe's busiest airports in 2017 by passengers:

1. London Heathrow – 78 million passengers, +3 pct
2. Paris Charles de Gaulle – 69.5 million, +5.4 pct
3. Amsterdam Schiphol – 68.5 million, +7.7 pct
4. Frankfurt – 64.5 million, +6.1 pct
5. Istanbul-Ataturk – 63.9 million passengers, +5.9 pct

ACI Europe said this ranking was likely to change in 2018 because Amsterdam-Schiphol had reached its capacity limits and growth at Istanbul-Ataturk was accelerating.