It's rare that representative airport located in a capital of West European country does not have a rail access to its downtown.
In 1990s, there were many airports in mega cities which don't have rail access. For example, Hong Kong's Kai Tak Airport didn't have railway station before opeing of the current Chek Lap Kok Airport.
One of the reasons would be expectation of opening Berlin Brandenburg Airport. It was initially scheduled to open in 2011.
Opening date was put off several times, due to many defects. I've heard that it was caused by many changes of its plan.
I felt how important it is to refrain from confusing subordinates by giving ambiguous instructions.