The link takes you (eventually) here: https://www.theguardian.com/commentisfree/2014/jul/24/avoid-air-travel-mh17-math-risk-guide. The comparison requires some conditions which are open to challenged. Fatalities per passenger-km may make sense in general, but is that really a good way to compare the safety of cycling with that of flying? Also, the risk of an air crash is only very weakly related to the distance travelled, as most accidents tend to happen near take-off or landing. (The chance of a bomb on board is also not related to the distance.)
But even if you can quibble on how exactly the comparison is made, it really would be a quibble to argue against the conclusion that for travelling a comparable distance, flying is safer than driving.