Air traffic controllers are striking in protest against staff cuts, which industry union UNSA said are unrealistic due to the operational needs of control centres.
UNSA also slammed the "considerable technological backwardness" of equipment used by air traffic controllers in France, as well as denouncing a "lack of investment" in the sector, according to French media.
The French Civil Aviation Authority called for the cancellation of a number of flights for all airlines using French airspace.
A number of flights between the UK and France have been grounded, and other routes across Europe have also been affected.
"Like all airlines, our flights to and from French airports, as well as those flying in French airspace, could be affected," Easyjet said.
"We are doing everything possible to minimise the impact of the strike on our customers, and have taken the decision to proactively cancel a number of flights, allowing customers to reorganise their journeys."
British Airways said: "Unfortunately in addition to cancelling some flights to and from France, other short-haul flights are also likely to experience delays throughout the two days, given how many flights would normally use French airspace.
"We will be using larger aircraft, where possible, to help affected customers and are doing all we can to reduce the levels of disruption."