By Joanna Plucinska LONDON (Reuters) -Chief executives of Europe's airlines called for more European Union support to increase the supply of green jet fuel and improve subsidies for its creation. The EU began requiring airlines to use more sustainable aviation fuel this year, with a 2% minimum blending mandate set to rise to 6% by 2030. "We have mandates but we don't have sustainable aviation fuel," said Luis Gallego, CEO of IAG, at a press conference for trade group Airlines for Europe on Tuesday. The ...