The exact flight time from Germany, the Netherlands, Austria or Switzerland to Oman, of course, depends on the exact departure airport. Direct flights, like the ones you can get from Munich and Frankfurt to Muscat, usually take about 6.5 hours. From Cologne / Bonn to Salalah, the direct flight takes a bit longer and is around 8 hours long. However, if a stopover has to be made, it can take much longer.
Especially for the destination of Oman, you should always look at the various flights on offer, because very few airlines offer direct flights. In general, you must take a stopover at the respective hub of the offering airline or at a partner airport. Depending on the airline carrier, a stopover flight may make sense. When it comes to the question of actual travel time, it always depends on how long the stopover actually takes. Therefore, the travel time for different offers can vary greatly. But if you decide to fly to Oman, a flight with a stop in Dubai, Abu Dhabi or Istanbul will make sense. In this case, the layovers are usually between 1 and 3 hours, and depending on the location of the layover, this could extend the trip and should be included in the total travel time. A stopover can increase travel time to 7.5 – 11 hours.