Using multiple certificates at one time?
 

I have two travel certificates with small values remaining on them ($39.40 & $36.60). I went to purchase a $158.90 ticket and had planned to use up the two travel certificates, paying the $82.90 balance with a large United gift certificate I have. Apparently I can only use 1 of the 3 at time. Is this right?

I didn't expect for both of the certificates to be able to be used at the same time, but I _did_ expect one of them plus the gift certificate to work.

Is there any workaround for this? It seems really silly that I should be expected to use my credit card to pay $119.50 when I have all of this United credit in various forms. Very annoying.