(Note: this post has been heavily-amended since I first wrote it)
I had missed the announcement last October that there are to be direct flights between Inverness and Dusseldorf weekly on Saturdays, operated by Lufthansa, during the summer months (July-September) of 2009; however, I did spot this today - workshops designed to help local businesses in the north of Scotland make use of the new route to Europe's wealthiest country; businesses need all the help they can get even at the best of times, but during the current recession/depression it may well be vital.
As for passenger traffic, I did a few sample journeys on the Lufthansa website and whilst the costs are quite high (about GBP250- to GBP270- depending on date, for a return journey), it involves a journey time of less than two hours and the flight times seem pretty convenient (mid-morning/early-afternoon). With luck these summer flights might help to bring in additional tourists from Germany and other nearby areas (in the Netherlands or Belgium most likely) to the north of Scotland and there will undoubtedly be those from here who could make use of this route, too, for trips to that part of Europe.
Even using Ryanair or easyJet to fly at that time of year (from Inverness via Luton or East Midlands) the costs would probably not be very much lower and the journey times would certainly be longer. NB/ However, closer study of these two websites shows their flights are completely impractical - where they exist - because either one would have to spend a night in transit, or get oneself to a UK airport not served from Inverness, eg. London Stansted.
PS/ I've just been checking the flybe website and indirect flights (via various places such as Manchester, Birmingham and Southampton) are available between Inverness and Dusseldorf for less than GBP100- in June this year; generally much longer journeys times, of course, than for a direct flight and naturally you have to contend with flybe's reliability record when considering the wisdom of some of the connecting flights.