TUI Group will decide by the end of May 2019 whether to implement contingency plans for the grounding of B737-8s for the peak summer season, Group CEO Friedrich Joussen told CNBC.

"We have to make decisions and we have communicated that we need to make a decision until the end of May in order to decide which of the scenarios is the active one. As a tour operator, we are bringing customers to their vacation and their holidays need to be secured. So we have actually secured capacity in the market in order to make sure that our customers can fly," Joussen said.

Joussen then went on to clarify that while the decision on the B737 MAX 8s will need to be taken by the end of May, the actual contracts for wet-leased capacity will gradually have to be extended after that date before mid-July, when the busiest time begins.

The travel group has also already opened talks with Boeing (BOE, Chicago O'Hare) regarding compensation for the grounding of the MAX 8s.

Currently, the TUI Group airlines have a total of fifteen B737 MAX 8s on the ground, including six operated by TUI Airways, four by TUI fly (Belgium), three by TUI fly (Netherlands), and two by TUI fly Nordic. TUI Travel has a further thirty-nine B737 MAX 8s and eighteen B737-10s on order from Boeing, the ch-aviation fleets advanced module shows.

TUI Airways is currently wet-leasing one B737-800 from ASL Airlines France, four -800s from Sunwing Airlines, two A320-200s from Titan Airways, and two A321-200s from Olympus Airways. TUI fly (Germany) wet-leases one A320 and A321 from Just Us Air and one A321 from White, the Dutch unit - one B737-800 from euroAtlantic Airways, two -800s from Sunwing Airlines, two A320s from GetJet Airlines, and one A320 each from Gowair Vacation Airlines and SmartLynx Airlines Estonia; the Belgian unit - two B737-800s from Air Explore, one A320 from SmartLynx Airlines, and two A320s from SmartLynx Airlines Estonia. The wet-leases not only cover the grounded MAX 8s and planned seasonal usual capacity increases as in previous years, but also the aircraft that were due for delivery between the grounding and the peak season.