Não se preocupe. Por exemplo, verifique link
I did not need to wear an extension when I flew last time - I am 5'9" and weighed 260ish pounds. I was in an 18-20 size clothes.
last time I flew, I was prob around 300 lbs. (or a bit higher) and I didn't use an extender. Never have actually, and my highest was 330lbs. Size 22 or 24 pants at lane bryant and I'm 5"6.