It has been done... as long as 90 years ago.

https://www.youtube.com/watch?v=bYtazEBQ1K8

The Short Mayo Composite of 1937 was a combination of two seaplanes - a large 'launcher' aircraft and a smaller, long-range mailplane. When fully loaded with its cargo and fuel, the mailplane was unable to take off under its own power; to allow it to take off, it was mounted atop a larger seaplane - a mothership - whose only purpose was to carry the smaller one into the sky. With their combined engine power, the combination could take off; once airborne and at altitude, the two would separate, with the mothership returning to base and the mailplane would continue to its destination.

The Soviets had been working on a similar experiment but with military applications. The Zveno project was a composite aircraft existing of a Tupolev TB heavy bomber and a number of parasite fighters. The Tupolev TB had a large carrying capacity but a relatively low speed which made it obsolete fairly quickly - it couldn't outrun fighters, and it was too slow to bomb heavily defended targets. Meanwhile, the Polikarpov I-16 fighter had a tremendous speed (for its time) but could not take off with heavy bombs, nor did it have the range of the TB. The Zveno project combined the TB bomber with a number of carried aircraft - Zveno combinations saw TB bombers fitted with anything ranging from two fighters (suspended from the wings) to five (three carried on top in addition to the two suspended ones. When taking off, the parasite aircraft's engines added to those of the TB to carry the combination into the sky, and their wings added lift. While both the TB and I-16 were obsolete by the time the Second World War arrived, the Soviets used the Zveno combination with success early in the war: they would have a TB take off carrying two bomb-carrying I-16s, and launch them near their target; the faster and nimble I-16s would perform a precision bombing of the target, while the lumbering TB remained out of the heavily defended area around the target. Afterwards, they would separately make their way back to base.

The losses of unescorted bombers in the Second World War, combined with the short-ranged nature of early jet fighters, led the US to develop its own parasite project in the mid-1940s. This saw the XF-85 Goblin emerge - a compact jet fighter that could be carried inside the bomb bay of a bomber, and that could be launched close to the target to provide fighter cover for the bomber during its attack. The only problem was that Goblin was very short-ranged so it not only needed to be launched, but also picked up again by its mothership, and that was where problems began. The airflow around the bomber provided a lot of turbulence for the smaller parasite fighter, and this made docking both difficult and dangerous. After a number of accidents and near-disaster, the project was abandoned, but not before lessons were drawn. It resulted in what would become the FICON project: a concept where a large mothership bomber would carry a parasite nuclear attack aircraft, which would be released at a distance of the target and then do a high-speed pass over the target, releasing its bomb before returning to be picked up by the bomber and flown home. While it was never used as such, the USAF did modify a number of reconnaissance aircraft in this way for intelligence gathering over the Soviet Union, however these encountered the same coupling difficulties as the Goblin had before - and when the long-range, high-altitude U-2 spy plane entered service, the FICON project was quietly abandoned.