Frankfurt Airport (FRA) is warning of a “massive disruption” to air travel this coming Monday after officials confirmed a 24-hour walkout. As Germany’s largest airport — serving 250 destinations with more than 80 airlines — it’s likely to affect flights within Europe and worldwide. Monday’s action is just one part of a national dispute over staff pay at airports across Germany. It is set to coincide with Munich International Airport’s (MUC) closure for commercial air travel March 26 and 27. There will be a double whammy of strikes on public transport Monday, as rail union EVG has also given the go-ahead for strikes. Here’s everything you need to know. Why…