Not all flights into Liberia have been stopped. I would know this as a pilot who flies commercial airliners regularly into Liberia. There are a lot of things for pilots to be worried about at the moment (air raid sirens going off in the middle of the night in the crew hotel in Israel, which warring countries are less likely to have ground to air missiles and how to pick our way between them, etc) but by far the biggest worldwide worry that we have at the moment is Ebola. Our crew hotel in Liberia is only a few hundred yards away from the main outbreak treatment centre. It will only take one person with Ebola to get on a flight to the UK to let the cat out of the bag. The man who made it into Nigeria by air collapsed at the airport - as someone who flies into airports all around the world I can tell you that even large African airports are still quaintly small compared to, say, Heathrow, or Schipol, or Frankfurt. The idea that someone with Ebola could find themselves in the passport control queue at one of these airports, vomiting (and bear in mind that this scenario has already happened albeit at a small airport) is frankly terrifying.
Also, patients are not being tracked down and monitored. This is precisely the main problem in west Africa atm. People are superstitious and if they find themselves with symptoms they are going into hiding as they fear being taken away to the treatment centre never to be seen again. The fact that they are being cared for and buried in secret, without decent infection control, is exactly why the outbreak has managed to carry on for so long there. Liberia and Sierra Leone are very primitive places, and it is difficult to educate the population and even more difficult to get them to act on any information they are given.
Sitting in Britain I am not worried that I am going to catch Ebola here at the moment. But if flights between Liberia, Sierra Leone and Europe continue, it is only a matter of time. And I AM worried about that.