Los Angeles. The future of the world grouping of 21 international airlines that includes South African Airways is under threat, as the US congress has become increasingly alarmed that disguised monopolies are emerging in commercial aviation. The Star Alliance network, which counts United Airlines, US Air and Lufthansa as its biggest members, is the biggest of the three codesharing networks, carrying 400 million passengers a year. Congress is sharply divided on the future of all three. Until now, the three have been given anti-trust immunity, which allows airlines to join and leave without being investigated for cartel and monopoly activity. Senior members of Congress want this to end within three years at the latest and have written to President Obama to enlist his aid. If anti-trust immunity is withdrawn, airlines wanting to join an alliance will have to go through such a tedious investigation that they will probably not bother. With political power now held by the Democrats, many politicians are suspicious of the alliance dominance, with some estimates putting the share of trans-Atlantic travel held by the networks at more than 80%. These suspicions have increased with the proposed alliance between British Airways and American Airlines, which want to join Oneworld, while Continental wants to join Star. Virgin's Richard Branson has stepped in, raising political temperature, by asking Congress to prohibit the BA-AA link. Casting himself as "a minnow", he has ignored his own alliances – leading to accusations of hypocrisy from his old enemy, BA. Republicans in Congress, being solid supporters of big business, say the airline industry is in such bad shape that the groupings are essential to ensure survival. Delta, now the world's biggest airline, lost $250 million in the second quarter alone and United $320 million. The recession has put the Democrats in a tricky spot. They want the economy to improve but don't want to encourage the greedy, rich-at-all costs attitude of the banks and finance houses associated with the George Bush days, which led to the financial crash in the first place. The most likely result is that pro-alliance politicians will try to spin out the wrangle in the knowledge that there are so many other urgent issues the issue will be forgotten and it will be back to business as usual.