ITC reversal treatment on prepaid invoice for personal use


Have a unique situation. Have bought a few flight tickets (Travel in June but payment done in April) for personal use from company vendor. He made a booking against GST number and the Airline has passed ITC on June booking in the invoice issued in April and reflecting in April's 2B.

Understand the ITC will need to be reversed in 3B under rule 42 in Row 4(B1) but since the supply is yet to be made (in June) when should this reversal be done (in April 3B or June 3B?). There is also another complication in reversing permamently i.e 4(B1) in April. That in case we decide to cancel the tickets the Airline will issue a credit note in subsequent months and since the ITC would already have been permanently reversed the credit note will have to be paid out of pocket.

In case this needs be reversed after the supply is made in June,  what should be the treatment of ITC available in April 2B? Understand that if it is claimed right now it will invite interest when reversed in June return. So in order to save interest can in Aprils 3B we should reversed as 'Others' 4(B2) and park amount in ECRS ledger for now and then recalimed in June 3B return in Row 4(A5) and 4(D1) and reversed in 4B1 at the same time? Also will any interest apply in such 4B1 reversal in June since ITC was never claimed but only Parked in ECRS ledger