When 617 Squadron (initially known as Squadron X) was formed in March 1943, Lancaster squadrons Bomber Command were requested to donate suitable aircrew for a special operation. It seems that crews volunteered or were recommended, either as full crews or as individual crew members.
The following list gives the 133 names of the aircrew that took part in Operation Chastise and the squadrons they were recruited from.


In addition, before receiving their purpose built Dambusting Lancasters 617 Squadron ‘borrowed’ 10 standard Lancasters from other 5 Bomber Group squadrons (as below) so they could immediately start their low-level training. Most were transferred to other squadrons as 617 Squadron received their dedicated modified Lancasters.
Three 50 Sqn Lancasters (W4112, W4196, and W4823) which had been delivered to RAF Scampton probably in preparation for the formation of 617 Sqn were all destroyed on 15 March 1943 when a 57 Sqn Lancaster (W4834) exploded when it was having its bomb load removed.

My other Dambuster / Lancaster related blogs:
Operation Chastise – The Dambusters a minute-by-minute account
https://pleszak.blog/2022/05/16/operation-chastise-the-dambusters/
THE HIGH PEAK DAMBUSTER
https://pleszak.blog/2022/02/12/the-high-peak-dambuster/
The day a Lincoln bombed a Lancaster, and a Meteor shot a Meteor shooting a Lincoln
https://pleszak.blog/2022/01/01/the-day-a-lincoln-bombed-a-lancaster-and-a-meteor-shot-a-meteor-shooting-a-lincoln/
Milk run over the Eder Dam
https://pleszak.blog/2020/07/13/milk-run-over-the-eder-dam/
Lancaster bombers operated by the Soviet Air Force in WW2
https://pleszak.blog/2019/12/05/lancaster-bombers-operated-by-the-russian-airforce-in-ww2/
What happened to the Lancasters used on the Dambuster Raid?
https://pleszak.blog/2019/08/20/what-happened-to-the-lancasters-used-on-the-dambuster-raid/
From Manchester to Lincoln via Lancaster – An aviation aristocracy family tree
https://pleszak.blog/2019/05/07/from-manchester-to-lincoln-via-lancaster-an-aviation-aristocracy-family-tree/
Testing and training for the Dambuster Raids – what’s left to see?
https://pleszak.blog/2018/06/13/testing-and-training-for-the-dambuster-raids-whats-left-to-see/
All the Dambuster Dams
https://pleszak.blog/2022/07/19/all-the-dambuster-dams/
Operation Chastise – The Dambusters a minute-by-minute account
https://pleszak.blog/2022/05/16/operation-chastise-the-dambusters/