When to book flight to Frankfurt or Munich

On Feb 12.

When we book with Delta, and it gets cheaper later ( I check with my AP every week) I call them and they give me a credit for the difference. It makes booking and getting the best seats kuch easier. Then we have a voucher to use for our next flight.

We prefer Delta and their partners. I have found that booking early usually gives me the more options and generally lower fares than booking later.
There is a direct flight from Atlanta to Munich that is great.

I am a 90 to 120 day out guy. I watch the fares and pounce when I see a good one. They change almost daily and sometimes quite substantially. The prices are about the same and the odds of resceheuling is less (hasnt happend to me buy once in almost 30 years).

Go to Google Flights and use the pricing charts to get an idea of the current prices on multiple dates. As others have suggested, book a flight with no change fees and then create an alert to look for a lower fare on the airline you book. I use American Airlines and have found that Frankfurt is almost always less expensive than Munich.

Let me clarify one thing. If the intent is to get from Poont A to Point B as cheaply as possible, the strategy of changing flights when prices drop may not be the best strategy.

I picked a flight on Lufthsnsa from FRA to Austin in May. It was the cheapest flight with one stop. The cheapest fare is about $750, with a checked bag about $875 The cheapest fare that has free schedule changes is about $1000. That ticket i doubt will ever be for sale for under $750. It might drop to $875 but that's a gamble.

Now if you fly Premium Economy or Business, that's s different story. On the flight I checked that would be about $2500 and about $5000. But you could save hundreds by rebooting when prices drop ..... or not if they don't drop.

Of you have a changeable ticket and the price drops, Great. Do it. But as a system for selecting tickets? You will do better at the tables in Vegas