Formation T/Os and landings, as has been suggested, need to be taught and practised regularly to keep current and safe. They are also inherently risky procedures, so that risk needs to be justified. In aircraft with decent A-A radars, radar trail is the way to go. I cannot really see when a formation T/O is justified in a modern FJ (if many years of recent OPS I have not seen a single formation T/O or landing, usually the jets are too heavy) and there are limited occasions when a failure may drive you to a formation landing (although in the vast majority all you need is a formation approach with the lead going round and leaving the runway for the #2). Not saying that we should definitely stop doing them but we do need to have a good reason, and not just because we used to do them. I know the Tornado DDH stopped form T/Os in the last few years of the jet, with good reason.