Variety of reasons for the wet leases, some proactively booked in the Autumn to cover the change from NAS to NAI at CPH, some to cover peak Summer production and allow (some ) to have summer leave..
Reactive leasing to cover late delivery of aircraft (capacity) some to cover training bottle necks due to additional training requirements for ETOPS required by the IAA on 737 LH
The dreamer liner deliveries are also running a little late requiring additional wet lease.
Yes it cost a fortune, but much of it should be one off costs and next year is planned slower growth, this year was colossal at around 32 narrow body and 12 wide body
737 Atlantic operations seem to be settling down.