Different results when using Selenium + Python

Question

I'm learning how to use Selenium with Python by trying to scrap Matrix ITA software (in case you don't know that, it helps to find good flight fares). I'm filling the whole form with Selenium exactly in the same way as manually (same airports, same dates, multicity: AAA-BBB,BBB-AAA,CCC-DDD).

When running the script I get completely different results. Manually the flight CCC-DDD is operated by airline X, when running Selenium - it is operated by airline Y. It dramatically changes the overall price of whole booking.

Why? I set up the same user agent as well as incognito mode. Is there any trick?