Investors voted with their feet in response to a surprise offer for T-Mobile US from Xavier Niel, the boss of low-cost French telecommunications company Iliad, which trades as Free.
Iliad’s shares slumped after it bid $15 billion dollars (11.2 billion euros) in cash for a 56.6 percent stake in T-Mobile US.
The French offer is seen as a long shot by some investors and analysts, but could lead to a bidding war with Sprint, the US mobile phone carrier now controlled by Japan’s Softbank.
Deutsche Telekom, T-Mobile’s majority owner, has not commented, nor has Sprint.
Iliad has shaken up the French mobile and broadband market in the past decade with its cheap, pared-down subscriber plans.
Its biggest advantage is that it would not face the competition issues that confront Sprint if it tries to merge with T-Mobile. They are the third and fourth largest US mobile phone operators.
The Federal Communications Commission and the US Department of Justice expressed a desire earlier this year to have at least two network operators competing against market leaders AT&T and Verizon.
On the downside, the French company specialises in broadband and lacks experience in mobile, T-Mobile’s main business, having launched its mobile service only in 2012.
It is also unfamiliar with the demands of competing in the United States, with its massive coverage needs and competitors with very deep pockets.