I just learned this myself the other day. Perhaps it is just me, but I have great difficulty redeeming these ecerts. Often times, I can book a cheaper fare not using the e-cert than with it...something about the e-certs can only be used on certain fares. I so much prefer the old United paper certs where an agent could book you on exactly which flights you wanted, and then the total value was just deducted. I also am still unclear as to what happened to the old United e-certs that have no promotion codes...they seemed to apply the cert against the base fare only and could only be used on domestic flights (even if received due to problems on an international flight).