The plume of ash from volcanic activity in Iceland is delaying flights once again—and creating an opportunity for one of the world's biggest discount airlines to undercut its main competition.

Air travel seemed to return to normal for a couple of weeks after the initial shock wave created by the volcanic eruption, but a number of European airports have shut down once again and hundreds of flights have been delayed this weekend due to drifting ash in Western Europe. This time around, with less airspace closure, landlocked passengers can hop onto a different airline's flight.

Especially if the flights are extremely inexpensive. Ryanair and easyJet, Europe's two largest discount "no frills" airlines, offer ridiculously cheap flights, oft at the expense of organization and timeliness. EasyJet is the beneficiary of this weekend's mess, though, opting not to cancel flights to destinations that Ryanair axed. A number of passengers have been able to rebook cancelled Ryanair flights with easyJet as a result.

It's hard to tell exactly why easyJet kept its flights running this weekend while its counterpart chose not to, and what the safety implications are—no one from Ryanair will speak to media outlets about the situation. We do know that the two airlines have a history of dirty competition with one another: The two have launched attack after attack, accusing one another of unfair advertising practices and libel. And EasyJet could probably use a boost after reporting a 7.6 percent decline from last year in the number of passengers in April.