Originally Posted by cheltzel

It is pretty easy to determine your odds, if you have access to one of the online tools that will show you the registration number for the aircraft operating a specific flight over time (I use FlightRadar24). You can look up ET575 and see how many flights are on 788s and have a registration numbers that start with ET-AOx or ET-ARx (the x is any other digit). If it does, the flight was being operated by aircraft with the angled-flat seats (and no wi-fi).

I've done that research several times (as my wife and I have flow ET574/575 a number of times) and I find that you get the angled-flat seats anywhere from 45% to 60% of the time. That being said our last two flights were on 77Ls with lie flat seats.

If you want better odds for getting a lie flat seat, I would look into flying on the morning flight out of IAD (ET501) or out of YYZ (ET553) as both have virtually no risk of getting angled-flat seats. Flying out of ATL is not as good (somewhere between 10% - 15% risk of getting angled-flat). Any other flights from North America on ET look pretty much like ET575 out of ORD as far as the equipment goes.