Very uncommon -- mind you, 4 x Business tickets are also rare as hen's teeth through Qatar redemptions and you somehow managed it. So never say never. But if I were looking for 4 Business redemptions on the same flight, Singapore Airlines would be my first port of call every day of the week.
Singapore redemptions have been going downhill lately.
I searched for multiple seats yesterday to Europe at the end of the booking schedule for a family trip in late 2026 and there weren't any options for x4 seats at the Saver rates. Only Advantage.
Previously this wasn't a problem if booking in advance.
