WOW air and other low-cost carriers based in Europe are responsible for much of the growth in transatlantic flights coming to or from the U.S. WOW air, which started flying in 2012, wasn't even serving the U.S. in the summer of 2014. Four years later it's expected to offer more than a million seats between the U.S. and Reykjavik, according to OAG. Many of those seats are being sold for as little as $99.
While some of the new flights to Europe are being offered by low-cost airlines, the legacy carriers have also been expanding their transatlantic schedules, especially in the summer.
Over the last five years, Delta, United and American have increased the number of summer flights to Europe by 11 percent. Some of that is because of stronger demand, but some of it is in response to other airlines adding service to cities where those legacy carriers have hubs or a major presence.
American Airlines decision to add daily service between Dallas-Fort Worth and Reykjavik shows the airline is prepared to protect its turf.
"We constantly evaluate opportunities for our network and summer travel has always been popular and fits with our network strategy," said Vasu Raja vice president of network and schedule planning for American. " We are excited to provide great service and connecting opportunities to Iceland from our DFW hub."
Harteveldt and others in the airline industry wonder if the growth in transatlantic flights can continue since they are being added by low-cost carriers who may get clipped by rising jet fuel prices.
"We don't know if all these airlines have financial staying power, so this may be a great summer for long haul low cost flights to Europe. We don't know what next summer will be," he said.
Questions? Comments? BehindTheWheel@cnbc.com.