Are aircraft capable of sustained inverted flight at constant altitude? Inverted flight as a part of manouveres, dogfights, acrobatics is fairly common but my question is:

Are any aircraft capable of sustained inverted flight without losing altitude? e.g. Could you fly 10 mins inverted at the same flight level?

To clarify: I'm not wondering about engines, fuel systems, air-frame strength etc. Fundamentally there's no reason why those systems cannot be engineered to be robust against inverted flight. 

What I'm curious about is specifically the aerofoil itself. 

i.e. As far as I can see, you'd need to balance the gravity vector with lift. 

Ergo, are aircraft wings generally capable of providing enough compensating lift in the "wrong" direction to balance gravity? Are all / most fighters / arerobatic certified craft capable of this?

We'd need an aerofoil that can provide a lift vector pointed in the +z direction normally but changable to a large vector pointing in the -z direction in response to a flight surface deflection?
Yes they are! Aerobatic aircraft can have symmetrical wing to improve inverted performance. So with these aircraft there is no any problem at all. Other agile aircraft, gliders can fly inverted as well. Of course is far from optimal but possible. Don't forget that lift depends of angle of attack as well. So if you fly inverted angle of attack and drag will be bigger to compensate for a "wrong" wing profile.