I assume you are talking about planes located in Italy, only 800 miles away. I think I read they could have been in Benghazi in less than 2 hours. But then what? Attack from the air? No, they would have to have landed...at the airport? Without Libyan permission? How does that work? And then what? Troops hitch-hiking to the consulate?
The White House and this President lied about this whole mess right from the get go. But, aside from preventing the attack, once it started they were pretty much helpless.
Obama didn't want those people dead. It messed up the the campaign stump fairy tale that he "had Al Queda on its heels" instead of admitting they were re grouping and gaining strength. What happened was inevitable.