The Republic of Singapore Air Force (RSAF) has been using the KC-135R aerial tanker for more than two decades, during which time air crew have established a strong rapport with it.
The aircraft were bought second-hand from the United States in 1997, and since then they have carried out air-to-air refuelling for international forces, taken part in humanitarian missions and joined the recent Defeat-ISIS coalition in the Middle East.
However, they are now being phased out and replaced with the new A330 Multi-Role Tanker Transport (MRTT), which made its first appearance at the RSAF 50th anniversary parade on Saturday.
The MRTT offers improved endurance, cargo and passenger capacity, and enhances the air force's ability to contribute to international humanitarian assistance and disaster relief (HADR) and peace support operations.
But their predecessors will be remembered fondly by those who flew in them.
"The KC-135R is a very reliable and versatile aircraft," said a second warrant officer, who cannot be named for security reasons. "It's like switching from an old car - it's sad that we now have to switch to another aircraft. "
The warrant officer, who was a boom operator on the KC-135R for about 15 years, has been deployed to the Middle East three times since 2015 as part of the Singapore Armed Forces' involvement in the Defeat-ISIS coalition.
The 43-year-old flew in missions to provide mid-air refuelling capabilities to coalition forces - which can prove tricky when foreign pilots are difficult to understand or are flying too quickly.
"I have to take charge during the refuelling process and be assertive, especially when safety could be compromised," he said.
As part of the KC-135R's capabilities, he is also trained to reconfigure it to evacuate casualties with a medical team within a few hours, fitting equipment such as oxygen supplies and batteries.
Meanwhile, a 40-year-old air force major told The Straits Times how he was involved in his first HADR operation after a magnitude-6.3 earthquake struck Christchurch, New Zealand, in February 2011. The KC-135R pilot and his crew flew in a Singapore Civil Defence Force urban search-and-rescue team and evacuated 32 civilians to Auckland. He said: "To put all we have trained for and what we have practised into action, it validated our training."
The primary role of the KC-135R is to provide air-to-air refuelling capability, thus extending the flight time of fighter aircraft such as the F-16 or F-15.
The pilot believes the ageing KC-135R still holds up well compared with other transport aircraft in the RSAF. "Speed-wise, it's equivalent to a civilian liner - we can cruise at Mach 0.8, so that's faster than a C-130," he explained. "In terms of reach, because of the fuel, we can push much further."