I flew with Norwegian Airlines a few months ago, a night from New York to London. During the day of the flight I received a text message saying my flight was delayed 4 hours from 11pm till 3am, and to ring to reschedule. I rang within minutes, and was told the only available flight would be 3am 24 hours later. Laughable. Then at the airport there we were delayed AGAIN so we didn't set off until gone 5am. I understand that delays and cancellations are common with Norwegian airlines. I followed up with them months ago but did not even receive a response from them. Yes they may be cheaper than other airlines, but you're likely to regret that choice.