class Airport(models.Model):
    iata = models.CharField()
    name = models.CharField()
    latitude = models.FloatField()
    longitude = models.FloatField()

class Flight(models.Model):
    origin = models.ForeignKey('Airport', related_name='origins')
    destination = models.ForeignKey('Airport', related_name='destinations')
    owner = models.ForeignKey(User)

[LHR, id__count=2}, {CDG, id__count=2}, {LAX, id__count=1}, {JFK, id__count=1}]

Airport.objects.filter(
    Q(origins__owner=user) | Q(destinations__owner=user)
)
.distinct()
.annotate(
    id__count=Count('origins', distinct=True) + Count('destinations', distinct=True)
).order_by('-id__count')