Most airline miles cannot be converted or transferred. When they can, the rate is often insulting to intelligence--like "If U give me a $10 bill, I will deposit $1 into your friend's acct. & keep $9 as my fee "."

DL is in Skyteam as is CO, whose miles can be converted to Amtrak, then onward to Hilton (25K per year limit applies.)

USAirways is also part of Star Alliance, but miles cannot be combined with SQ.

ADVICE: Just start fresh with DL & use up your other miles &or make sure to credit a car rental or hotel stay to each program once in a while, because most miles expire in 3 years of total inactivity. U never know where work will send U when the Atlanta project is done.