On 5 April 2019, MINDEF submitted a request to purchase F35Bs from the US - to acquire four planes with an option of an additional eight more, subsequently. The Congressional Notification (CN) of Singapore's request of purchase adheres to the formal requirement within the US for possible sale of military equipment to foreign countries. It is routine and Congress has 30 days to respond to the CN. The CN is not a formal contract of purchase. If the CN passes, formal terms will be negotiated for the Letter of Offer and Acceptance.