Boeing has added firm orders for 20 777X and 19 787-10 aircraft to its backlog.
The 23 June update on the manufacturer's orders and deliveries website appears to be a confirmation of a commitment announced by Singapore Airlines on 9 February.
SIA's letter of intent covered 20 777-9s and 19 787-10s.
Asked about the status of SIA's commitment on 22 June, Boeing sales vice-president Ihsanne Mounir replied: "Look at our website tomorrow."
The orders for the 777-9s and 787-10s have appeared on Boeing's website with the customer listed as "unidentified".
SIA plans to receive the 777-9s in 2021, a year after first deliveries of the 787-10s. The 787-10 commitment included model-conversion rights.
The airline committed to power the 787-10s with Rolls-Royce Trent 1000 engines. GE Aviation exclusively powers the 777X fleet with the GE9X engine.