I think that if someone became symptomatic during a flight from an affected country, they would not leave the airport outside of an ambulance. And then they would get better medical care than they could have expected back in Africa, and have a better chance of survival.
I question whether someone seeking to enter the US illegally would have the means to buy an airplane ticket.
Infected person becomes symptomatic on the trip, infects others, dies or is left behind. Figure that is the end of week 1.
Newly infected people keep up for up to two weeks, infecting the third wave, so to speak, as the group picks up members.
Those who sicken are left behind.
The newly infected continue on, the coyote picks up more people, lather rinse, repeat.
It isn't a question of whether the initial infected person makes it across, but whether the disease does. After all, their mission is to get the outbreak here, not the individual.
The subsequently infected individuals are the transfers and connecting flights for the virus. No plane needed.
I also question the timeline of 40+ days, when we had kids showing up at the border wholesale after taking the Beast through the country.
Certainly a terrorist organization would be able to do far better logistically, and get the first person or the second group into the country by having them join the group closer to the border.
They have Billions of dollars at their disposal, and that makes wheels turn faster than they will for the average peon.
Just because somebody does not have permission to enter the US, doesn't mean he does not have money. Coyotes charge $3,000 and up to get somebody over the border, and find plenty of customers.
Now, consider what happens if there are a number of Ebola infections in Mexico, and how much Mexicans who think they may have been exposed would want to get into the US and have access to US medical care?