Long-haul flights of that duration (and longer!) are currently
being operated by many airlines. It's actually quite tolerable,
even in economy class, if you can find ways to keep yourself
occupied, and assuming you don't get seated next to a mother and
her screaming baby. 
A trip to Singapore for me would involve a 14-hour flight from
Minneapolis to Tokyo, and then a 7-hour hop from Narita to
Singapore. Hasn't killed me yet...
