It's the same reason why last summer, London and Dublin saw stupid-low fares. This year the torch has been passed to Spain and Italy. Cheapflights' data shows that the average fares to popular cities in those countries have deflated like a bag of chips the second you open it. Booking 90 days out, the average Barcelona flight fell from $1,075 in 2016 to $631 this year (down 41%); Madrid went from $1,018 to $693 (down 32%); and Venice (minus-31%) and Rome (minus-27%).
These are just averages; it's possible to find flights to any of these cities from New York for 300-something bucks. If these fares were elevators your ears would be popping. Next year it might be Paris and Amsterdam. It just depends where the discount carriers decide they want to converge.
"Barcelona is another perfect example of collision of a lot of different airlines coming into play," Fisher says. "So now instead of just looking at Delta or United to get a flight to Spain, you've got TAP, airberlin, Aer Lingus, layered on top of deep-discount carriers like WOW and Norwegian."