It's a complex matter. Subsidizing single companies, like say, a national airline, is explicitly forbidden, under the principle of "level playing-field"; but su

It's a complex matter. Subsidizing single companies, like say, a national airline, is explicitly forbidden, under the principle of "level playing-field"; but subsidizing an entire sector is typically not forbidden, as long as the market is open and subsidies don't discriminate. In practice this is gamed in many ways, and there have been winners and losers.