I think Nessbounder is too used to Lucario. Now he thinks lingering hitboxes are the greatest things ever and are the defining factor of a top tier character.
Which clearly isn't the case since MK and Snake really don't have lingering hitboxes.
And Lucario who does have them clearly isn't top tier.
Snake has very good lingering hitboxes actually. On most of his moves. Especially Utilt and Ftilt. Not to mention his Bair and Uair.
And to answer your question: Fair is an aerial. It may have lag canceling on landing, but the lag is still there regardless. It can still be shield grabbed most of the time, and even shield-released and jabbed. Of course, this is only if you're using it on a grounded opponent, which is unsafe for most aerials.
I personally don't find Ftilt all that effective. There's clearly a bit of lag after the move ends taking the IASA frames into account (although barely any startup time kind of negates this.) Look at Lucas's Ftilt and how much faster it is in comparison lag-wise. That's a really safe Ftilt right there (although it doesn't have so much range.)
I'm not going to argue with Dtilt because that move really is very safe and awesome, but like all dtilts, you have to sit through the crouching animation, which cuts the speed of the initial jab slightly, but nothing big. Even then, it's got a very low hitbox that can be shorthopped over, so you can't exactly spam this move against a clever opponent.
I don't know where you're getting this thing about me thinking that lingering hitboxes are the defining point of a top tier character...but they are important. Look at Olimar. Little freak has lingering/multiple hitboxes coming out of every orifice of his body and they're incredibly annoying. Even Toon Link has some lingering hitboxes on his sword. I never once said that Lucario is a top tier character. I think he's a high tier, or possibly the very lowest of top tier, but not a defining top tier character.
My appreciation for lingering hitboxes goes way back beyond just the Smash bros series.
And Sonic Wave: One of my only regular human opponents plays Marth and Metaknight commonly. You also have to realize that as a Lucario/PK boys player, spacing is just as important for my characters as it is for yours. I also play a decent Marth myself, although I just don't like him as much as the other sword characters.