How do I give human fighters a chance when fighting much faster and technologically advanced alien craft?

Question

Human fighters in this instance are six WWII Spitfire Vs and one B-17 Bomber modified with two extra turrets. Each of these planes has been refitted with shields, which can protect from 2 shots on the fighters and 12 on the bomber. The bomber does NOT drop bombs, but instead has what is basically an energy grappling hook turret on the bottom which can be used to tow or be towed or stick fighters to each other. Each of these planes have a gravity engine capable of speeds of up to 100 m/s(~220 mph) for short bursts, and a maximum sustainable speed of 70 m/s(~150 mph). The gravity engines can also be used as a short range offensive weapon, temporarily turning the planes to propeller propulsion and creating a strong gravitational anomaly for a few seconds, capable of diverting enemy fire, quick maneuvers, and if done right even imploding enemy craft. Fighters are armed with four machine guns, bomber has two top turrets, two bottom turrets, four side guns(two left two right), and one rear turret, all of which are machine guns.

The enemy craft are alien spacecraft armed with energy weapons and have shields designed for protection against energy weapons, which is one advantage the humans have. Since the fighters and bomber use physical projectiles, the shields quickly fall but a lucky shot is required to disable a key system or kill the pilot, or they could swish cheese it but that takes a lot of ammunition. Enemy fighters can travel at speeds up to 400 m/s(~900 mph).

So even though the humans can easily take down enemy shields, a lucky hit or missile is needed to completely disable the enemy craft. Since the former is rare, and the latter is in short supply, they get stuck in extremely long dogfights which can have very bad outcomes for humans. And then since the aliens can go about 6 times faster than them, the humans don't really get to decide the battlefield. Are there any ways I can have the human ships stand a chance against these aliens, preferably without changing the human or alien ships?

Reason why military fighters aren't zooming around shooting everything-

Since the aliens first started attacking, military fighters were the first thing to go and were quickly shot. These WWII planes were donated by some crazy rich old guy and crammed with whatever alien tech would fit and some machine guns, so they're some of the last airborne units around.

Answer 1

Crypto Analysis

Humans have advanced mathematicians on the ground who are able to break the enemies communication. Allowing them insight into what the enemy is planning, and able to ambush them.

If your audience is ww2 aviation enthusiasts the Ultra metaphor (Enigma codebreaking) should be a good fit.

Answer 2

If the aliens are particularly vulnerable to projectile weapons, how about an even older weapon: Case Shot

Basically this is the cannon or artillery equivalent of a shotgun, though typically with large pellets. And sometimes with different objects. (There is a notable case of using cheese.) Any small objects that could damage the aliens is a good candidate.

Strangely, with the speed variations, there is one other possibility: Just spread a debris cloud for the alien ship to run into, and let their ship, rather than the projectile, provide the speed difference.

One extra problem for you: an alien space vessel should actually be well defended against projectiles. They run into them at high speeds all the time - orbital debris, micrometeorites, etc... (I suppose their fighters could be atmospheric craft that don't have this requirement.)

Answer 3

Flak Rounds

"American troops knew that the greatest single weapon of the war, the atomic bomb excepted, was the German 88 mm flat-trajectory gun, which brought down thousands of bombers and tens of thousands of soldiers. The Allies had nothing as good, despite one of them designating itself the world's greatest industrial power."

— Paul Fussell, 1989

Flak rounds fly to their target and then explode into a cloud of high velocity shrapnel. I would imagine a cloud of metal fragments would quickly overwhelm an energy shield and destroy the fighter.

The fighters use energy weapons because they have an effectively infinite amount of shot and since they don't need to carry ammo are much lighter and faster. The downside is a reduced range when in a planet's atmosphere.

Humans using flack cannons have a greater range than energy weapons and can use the cannons as a deterrent to keep enemy fighters away but if they run out of ammo, are easy prey for the faster fighters.

The enemy needs to keep the humans firing to use up the ammo but avoid getting hit leading to false charges and retreats while the humans need to conserve ammo and shoot only when sure of getting the enemy fighter.