As another commenter mentioned, this is exactly what we're building at Adioso (YC W09). It turns out it's very hard to do for reasons mostly to do with decades

As another commenter mentioned, this is exactly what we're building at Adioso (YC W09). It turns out it's very hard to do for reasons mostly to do with decades-old technology and business conventions in the travel industry. This is why it still barely exists, even though so many travellers want it. But we're making good progress. Stay tuned.