[
    {
        'flight_id': 'f123',
        'pax': 234,
        'airline': 'Foo Airways'
    },
    {
        'flight_id': 'f124',
        'pax': 200,
        'airline': 'Bar Airways'
    }
]

{
    'f123': {'pax': 234, 'airline': 'Foo Airways'},
    'f124': {'pax': 200, 'airline': 'Bar Airways'}
}

flights = dict((f.pop('flight_id'), f) for f in flights)

flights = {f.pop('flight_id'): f for f in flights}

>>> d = [
...     {
...         'flight_id': 'f123',
...         'pax': 234,
...         'airline': 'Foo Airways'
...     },
...     {
...         'flight_id': 'f124',
...         'pax': 200,
...         'airline': 'Bar Airways'
...     }
... ]
>>> itms = [x.pop('flight_id') for x in d]
>>> dict(zip(itms,d))
{'f124': {'pax': 200, 'airline': 'Bar Airways'}, 'f123': {'pax': 234, 'airline':
 'Foo Airways'}}