I used to mock the crap out of flat-earthers. Then I basically became one—after YEARS of investigating it with a sincere heart, and just not getting there. SO, I'm on your side… and I STILL find this argument to be one of the absolute worst. It's worse than saying nothing at all. A plane literally has it's nose up nearly all of the time during the landing process…as it is DESCENDING. A bird's wings are angled UPWARD even as they come in for a landing.
Every has ridden in a car with their arm out the window and made an "airplane" out of their hand. You will find perfect equilibrium (where your hand doesn't want to "dive" or "take off" at a slight upward angle, just to counter the weight of your arm/hand. I plane is typically going to be angled nose-upward a little whether ascending OR descending.
This argument SUCKS, except to people who don't understand how things work, which sadly, is A LOT of flat earthers. That's not to mock unintelligent people, because A LOT of "smart people" believe a lot of ridiculous bullshit with which they've been indoctrinated by "institutions of authority" and a lot of "dumb people" believe things the intelligencia think is retarded, but just happens to be right.