Back in July 2009, I received an E-certificate. At the airport, the gave me a number because the flight had to be postponed. They did not give me a paper certificate, only a number to put on paper. I received a number that began with the usual numbers for E-certificates. I have had no reason to fly until this year again. On united.com, I entered my E-certificate number and it said I "already redeemed the certificate". I contacted a representive from United, and they told me that my certificate got redeem in late 2010, though that's not true at all. I'm thinking it possibly expired? They did not tell me that the E-certificate had an expiration date, though I'm curious if E-certificates have expiration dates? I'm not a frequent flier, that's reason I don't know the entire details about this stuff. I assumed that I could use this certificate at any time, though it's starting to seem that it's going to happen. I'd really like go on a trip this year and had hope that I could possibly use this to help cut expenses.