We noticed this sale on United's site, supposedly offering discounted fares to Europe for spring travel. So we searched several routes and were disappointed. Just one example: Denver to Budapest for $362 each way plus tax. We tried leaving May 5 and returning May 12, and got a fare of over $1500 on United.com (code shared with Lufthansa). But using a 30 day flexible search on Orbitz (using a stay of 7-10 days, searching May 1-30) we found $903 RT incuding tax on British Airways via London on the same dates.
That's why we always suggest that you do a flexible date search using Orbitz and then compare the results on individual airline sites.