One mission - several combats
As a consequence of Allied numerical superiority in the air over Normandy in 1944, the Luftwaffe was instructed to operate in "Gefechtsverbände" - intended to consist 40 or more fighters, but in reality, due to circumstances often composed of rather only half that number. These became subject to repeated Allied fighter attacks from several units.
Author Nick Beale wrote: "Ultras from the Jagdkorps II in Normandy campaign give the impression that Allied superiority manifested itself as a near-constant presence - i.e. the Luftwaffe was often lucky to get to its target (or off the ground) without running into opposition. The refrain seems to have been 'task not carried out owing to …' "
What was even worse - from the German POV - was that already the first combat during a mission caused the German formation to get dispersed into twos or threes - hence a US 8th AF observation: "enemy aircraft were sighted . . . mostly Me 109s and Fw 190s in twos and threes". These twos and threes then often were left on their own, with tired pilots and aircraft running low on both ammunition and fuel - against "fresh" Allied formations of 20, 30, 40 or more fighters which bounced them from above. (An air combat often has the tendency to drift downward in altitude, so that fighters which have come out of one combat often are flying lower than newly arriving fighters.)
One example of the fate of such a Gefechtsverband is given on 27 June 1944. The largest single mission performed by the Luftwaffe over France on 27 June 1944 probably was that which involved I. and II./JG 27 in the evening, with approximately 20 Bf 109s. These were attacked by the Thunderbolts of 353 FG, and then Thunderbolts of 56 FG joined in, followed by the Mustangs of 352 FG and 355 FG. It is possible that the Mustangs of 339 FG also participated in the onslaught on I. and II./JG 27's formation, since this fighter group claimed a victory against a German fighter in the same area and at the same time, while there are no records of other German fighter units in the vicinity by the same time. The Germans lost nine Bf 109s (the Americans claimed 14 victories) while they only managed to shoot down two US fighters. (See Clark, "Angels Eight", p. 94, and CD for 27 June 1944.)
In total, there were 134 Fw 190 and 196 Bf 109 sorties over France during 27 June 1944, in thirty-five ordered missions. "It is probable that a 'mission' in this context represented an effort by one Gruppe; a Gruppe mission thus contained an average of fewer than ten aircraft." (Don Caldwell, "JG 26 War Diary", Vol. II, p. 292)
Examples of Allied numerical air superiority
Some interesting examples of the vast Allied numerical superiority over France during the invasion of France is given by the combat reports which are published in 20th FG's chronicle, "King's Cliffe: The 20th Ftr. Grp Association":
On 25 June 1944 in the evening, a formation of 49 Lightnings from US 20 FG attacked 15 Bf 109s near Chartres. ("King's Cliffe: The 20th Ftr. Grp Association", p. 161.)
The US report from the mission against targets north of Paris on 28 June 1944, shows a total of 25 German fighters intercepting 684 heavy bombers escorted by fourteen Fighter groups with a total of 569 fighters. US 20th FG, with 46 Lightnings, was attacked by eight Fw 190s and Bf 109s. ("King's Cliffe: The 20th Ftr. Grp Association", p. 162.)
The report for 14 July 1944 reads: "This morning 524 P-51s and P-47s were dispatched to support a special heavy bomber operation in the Chartres area. Enemy opposition was characteristically meagre and 4 of 10 Me 109s and Fw 190s encountered were shot down by our fighters."
Fighting against heavy odds
Of course the Allies weren't always able to make use of their numerical superiority. To quote Don Caldwell again, this time concerning 18 June 1944: "Addi Glunz took Uffz. Lissack, a young 7th Staffel pilot on a two-airplane evening sweep. They encountered a pair of tactical reconnaissance Mustangs from No. 414 Sqd. (RCAF) and shot them both down. The more experienced of the Geschwader's pilots could best most Allied pilots in single combat, but such opportunities came rarely." (Caldwell, "JG 26 War Diary", Vol. II, pp. 281 - 282.)
In other cases, the numerical superiority would not save the Allies from sustaining bitter losses - like on US 4th FG's last mission on 6 June 1944. David Clark writes that "P-51s of 334th FS, 335th FS and 336th FS of the US 8th AF 4th FG tangled with 10 Fw 190s. . ." ("Angels Eight", p. 42.) I don't know why Clark states that 10 P-51s were lost - due to "mechanical failure, a collision and heavy flak". 4th FG's report clearly states that there were "only" seven losses, and that most - if not all - were shot down by German fighters:
"Fifteen 109s and 190s bounced them out of the cloud cover. The entire section, consisting of Bernard McGratten, Harold Ross, Walter Smith, and Cecil Garbey, was shot down and all four pilots were killed. Later, at 2035 hours, Edward Stepp was heard over the radio to say to Mike Sobanski "Watch those behind you White Leader!" after Sobanski had requested a visual check of his aircraft after hitting some wires. Both were killed. As if that were not enough, Mike McPharlin, who was visiting his old squad, the 334th, on loan from the 339th Fighter Group in his 6N-Z, was lost after reporting his left magneto was out and he was aborting. He wanted to fly "the big one" with his old buddies. He was never heard from again. The totals for D-Day, 4 destroyed, 9 lost. Seven of the losses were on the final mission of the day."
Obviously, Clark made a mistake when he placed this disastrous combat at "just after noon", since the 4th FG report clearly states that it was "The last mission of the day [which also] was the worst for the 4th since its inception when 12 Spitfire MkIXs were lost near Morlaix, France"- i.e. at between 2030 and 2100 hours.
The "fifteen 109s and 190s" which bounced 4th FG clearly were a composite formation from JG 2 and 2./JG 26, led by Hptm. Herbert Huppertz. These German pilots claimed six Mustangs, one Thunderbolts and three Typhoons during this mission (of which Huppertz contributed a Mustang and a Thunderbolt). In all, these German pilots were engaged by at least the Mustangs of 4th and 352nd FG, the Thunderbolts of 56 FG, and Typhoons of 2nd TAF. Probably they were engaged by even further Allied units on this day - when the Luftwaffe fighters in France performed a total of 172 sorties throughout the day (divided between at least 13 separate missions from 0800 hrs to midnight ), versus 14,674 Allied sorties (including 2,185 by US 8th AF fighters) over the landing region.