Angels do not have any feeling for modern technology. Their millennia long studies of nature however has given them profound knowledge that some would say borders to witchcraft. The skill of Angels to absorb the strength and ability to fly of their dragon is one of them.
It takes a lot of strength and experience to do this process. And the dangers are noteworthy.
That 's why only the older Angels can and will execute it. Even more, it is forbidden for novices.
Experienced Angels are capable of reversing the process at will. During the time the Angels have absorbed the powers of their dragon, a dragon is weaker and more susceptible to influencing.
Angels having gone through this process show large feathered wings.