A word of caution: United has changed their policy since Richard's experience last year. United will no longer accept a pet as "checked baggage" or "accompanied baggage".

The pet has 2 options: 1)travel in the cabin with you if small enough (well, except for the pig incident) or 2)fly "unaccompanied" as part of the cargo/air freight system but only if shipped by a "known shipper". A known shipper is someone with an air freight account with UA. Pet shipping services like ipata.com also qualify. Although the UA web site says that they accept cargo from licensed pet/commercial breeders, UA's cargo dept says that is incorrect. In general, fewer airlines are shipping animals these days possibly because it's such a resource intensive and risk filled effort. UA has also said that stricter FAA security guidelines led to the change in policy. I've travelled with dogs a few times back in the days when UA allowed it and always had good experiences.

I'd buy my dog a ticket in first if UA would let me - I'll bet she'd love those mustard pretzels.