"Company slogans" joke

A class professor was giving a lecture on company
slogans and was asking his students if they were
familiar with them.
.
"Joe," he asked, "which company has the slogan,
'come fly the friendly skies'?"
.
Joe answered the correct airline.
.
"Brenda, can you tell me which company has the slogan,
"Don't leave home without it?"
.
Brenda answered the correct credit card company with
no difficulty.
.
"Now John, Tell me which company bears the slogan,
'Just do it'?"
.
And John answered, "Mom...."