Good question, good observation, good attitude. Well done!

For a start, here is a site that discusses the matter better than most; beware sites where the participants are partisan! Even when they do not speak total nonsense, they tend to be so biassed that their opinions are misleading at best.

Yes, aircraft can fly upside down (by and large!) Yes, the Bernouilli effect does count in most designs. (I understant that some fighters, including the WWII Mustang actually had symmetrical upper and lower wing profiles, so it seems that some high-performance aircraft at least, did reliy exclusively on angles of attack.)

However, I like this site; it is unemotional and discussess a number of considerations in a balanced way. Come back by all means if you are left with more doubts; nothing ever is final in science and technology.

http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/angatt.html

Most people have held their hand out of a moving car window and noticed that by experiementing with different hand positions it is possible to produce an up or down force on the hand. The majority of the force being felt in this case is not 'lift' but the buildup of high pressure air against the surface of the hand due to the air particles becoming compressed as the hand rams against them. As the angle between the hand and the airflow (i.e. the angle of attack) increases, a greater surface area is presented to the air thus compressing more air particles, increasing the pressure and therefore size of the force. So as the correspondent notes, the change in angle of attack has a significant effect on the amount of upwards force being produced. However, at the same time it is possible to note that as the angle of attack increases, a rearward force becomes increasingly apparent to the point where eventually it is the only force being felt. This rearward force is known as drag. Drag opposes the forward motion of the hand so as the angle of attack increases, the car’s engine must work slightly harder to maintain the same speed. Whilst this drag is easily overcome by the car’s engine and the only penalty is a slight reduction in fuel economy and top speed, in aircraft, where propulsion is less easily achieved and weight is critical, drag penalties are much more significant.

So it is clearly desirable to maximise the upwards force being produced whilst minimising drag. This is where the airfoil comes in. Due to the shape of the airfoil, which causes air passing over the curved surface to move faster than the air over the straight surface thus creating an area of low pressure over the curved surface (Bernoulli’s Principle), the airfoil generates lift. This lift is generated even at zero angle of attack and indeed if an aircraft is moving through the air quickly enough, sufficient lift may be generated by the airfoil alone to entirely support the weight of the aircraft. At lower airspeeds it is necessary to introduce a small angle of attack in order to combine the upwards force produced by high pressure air with the lift generated by the airfoil to produce enough total upwards force to support the weight of the aircraft. This is why aircraft coming in to land, when it is desirable to fly as slowly as possible, appear to be pointing upwards when they are actually descending. Higher angles of attack also effectively make the air passing over the curved surface of the wing travel even further than the air on the straight surface thus increasing the speed, reducing the pressure further and increasing lift.

Most aircraft can fly upside down but flight is usually very inefficient this way and high rates of descent normally occur. This is because the wing has to be presented to the air flow at a very high angle of attack to compensate for the fact that the airfoil is producing little or no lift to support the weight. Some aerobatic aircraft use symmetrical airfoils that have the same shape on both sides which enable the aircraft to fly equally well either way up but overall the wing produces less lift than a conventional airfoil. Indeed, at zero angle of attack a symmetrical airfoil produces no lift at all so it must be flown permanently at a higher angle of attack than is normally necessary.

Aircraft, particularly airliners, are usually designed so that they are flying most economically at their intended cruising speed so the Jumbo in question would probably be producing nearly all of the lift it requires purely from the shape of the airfoil and zero or very little angle of attack.