Ever since TUI AG in 2008 shifted its focus away from shipping and decided to sell a majority stake in Hapag-Lloyd, its shareholders have been considering ideas of how to combine TUI AG and TUI Travel to reduce overhead costs and increase combined use of resources, such as hotels.

While TUI AG has said it wishes to focus more on tourism, its management has always refused to comment publicly on options for TUI Travel.

Both groups currently have their own headquarters - in Hanover, Germany, and London respectively - and a merger could potentially yield over 500 million euros ($667 million) in synergies, two sources said.

Analysts, however, have calculated a much lower number closer to 100 million euros.

“The figure would be substantially lower for the hypothetical case that TUI Travel buys TUI AG,” Commerzbank analyst Johannes Braun said.

TUI AG’s two biggest shareholders, Russian tycoon Alexey Mordashov with 25 percent and Norwegian shipping magnate John Fredriksen on 15 percent, have lost millions on their investments in TUI AG, after building their stakes in 2008 and 2009 for a premium to today’s share price.

The sources said a decision on any deal was not imminent.