Financial terms of the sale weren't disclosed but the arrangement is expected to be completed by the end of this year.
"Thales will continue to develop its military system capabilities, which remain part of our key product portfolio," said Marion Broughton, head of Thales UK's aerospace business.
"Thales will continue to develop its military system. However we feel that L-3 Communications Link Simulation and Training UK Ltd. will be better placed to maximize the potential of the civil simulation business."
Thales' civil fixed-wing flight simulation business specializes in high-end simulation equipment for major airlines and aircraft maintainers worldwide.
Included in the transaction is Thales' flight simulation training center Thailand.
Also under the agreement, Thales and L-3 will work to ensure a supply chain for civil components that Thales may need in its military business.