There may be bigger airports with more routes, but still, despite its congestion and bursting at the seams capacity issues, London Heathrow still holds 8 of Europe’s top ten routes.

1. LHR- JFK New York is the busiest route out of Europe with almost 3,000,000 annual passengers, heavily dominated by BA and American who between them carry some 60% (BA 40 American 20). Virgin Atlantic manages nearly 29% with Delta just over 10%.
2. The JKF route jumped to first because the busiest route prior to that was LHR-DXB. That fell from over 3,200,000 to under 2,675,000 because both Qantas and Royal Brunei stopped flying via DXB. Qantas went via Singapore and Royal Brunei started flying the Dreamliner direct.
3. LHR-Dublin, Ireland. This is entirely operated by IAG through BA and Aer Lingus, with a 65:35 split in favour of BA. Frankly its an atrocious situation when one airline group gets to hold a complete control over such a busy route.
4. Istanbul-Tehran with an increase of almost 10% in passengers between the two airports. It now tops over 1,745,000 people a year.
5. Heathrow-Amsterdam Schipol grew by 3%  to 1,727,000
6. Heathrow-LAX is now running at over 1,612,000
7. Heathrow-Singapore is approaching 1,600,000 up nearly 16%
8. Heathrow-Hong Kong nearly 1,550,000
9. Paris CDG-Madrid at 1,311,000
10. Heathrow-Mumbai up 15.5% at 1,112,000 passengers

Fastest growing routes include Palma de Mallorca-Düsseldorf, Zurich-Berlin Tegel, Heathrow-Singapore (largely because of the Qantas re-routing), Madrid-Paris, Amsterdam-Dublin and Istanbul-Tel Aviv Ben Gurion in Israel.