Find the list of all possible distinct destinations, with at most one layover, departing from the base airports of airlines from Germany, Spain or Canada that are part of the “OneWorld” alliance. Include both the destination and which airline services that location. As a small hint, you should find 158 destinations.
The only constraint is that the starting airport is the base airport of a selection of airlines. Nowhere is it mentioned that the flights must use airlines of the OneWorld alliance, the only restriction is on the starting airport.
Yet in the detailed answer:
After this, we’ll unwind our connections array, and then use $project to add a field representing whether this particular route is valid, meaning it is a route flown by one of our desired carriers.