Technically yes. But I am unaware of any attempt to do this with airliners.

But there were several designs in the past which used a big airplane or a Zeppelin as a mother ship, which took fighters with it for air defense. The [B-36][1] was involved in several such designs.

![enter image description here][2]

In all cases the docking was made from below, because this gave the fighter pilot the best field of view and reduced the risk of a tail strike.

While the fighter in the picture above is a Republic F-84, McDonnell even desiigned one specifically for the purpose of being carried around by a bomber, the [XF-85 Goblin][3]. It used a rather complicated trapeze for docking and was then pulled up into the fuselage, as the picture with a B-29 below shows.

![enter image description here][4]

Your design proposal with the simple platform on top of the fuselage would carry a high risk of a tail strike if anything goes wrong, so it is unlikely that this will ever be tried in real. But when you change the airliner to a AN-225, the idea looks not totally impossible. The [Russians tried to dock a fighter][5] with a mothership as early as the 1930s. The picture below shows a TB-3 docking with a I-Z fighter, the first pair of aircraft in history to dock in flight.

![enter image description here][6]

The main reason for docking was the much smaller range of fighters. Today, air refuelling takes care of this deficit, so it is unlikely that anyone will see a benefit strong enough to justify the expense of modifying two aircraft and the risk incurred in the docking process.


  [1]: http://www.nationalmuseum.af.mil/shared/media/photodb/photos/050324-F-1234P-011.jpg
  [2]: https://i.sstatic.net/2n1IR.jpg
  [3]: http://www.google.de/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/4/41/McDonnell_XF-85_Goblin_and_EB-29_mothership.jpg&imgrefurl=http://en.wikipedia.org/wiki/McDonnell_XF-85_Goblin&h=981&w=1800&tbnid=2YxZQpyKyLbV8M:&zoom=1&tbnh=90&tbnw=165&usg=__0YhmMxzK6XfAoLHA1bERsTTp0EY=&docid=4wR9UaZpTNx14M&client=safari&sa=X&ei=6adwVM-XBYuBPZOmgJAM&ved=0CCsQ9QEwAg&dur=418
  [4]: https://i.sstatic.net/EFUMl.jpg
  [5]: http://en.wikipedia.org/wiki/Zveno_project
  [6]: https://i.sstatic.net/qcGq8.jpg