The problem the planners solved in 1950 was simple. The direct great-circle route between Sao Paulo and Manaus runs through nothing - or, rather, through some of the densest and most uninterrupted rainforest on the continent. Before Cachimbo opened, there was no middle waypoint. A reciprocating engine failing halfway across meant a long glide to somewhere that was likely not an airstrip. Cachimbo gave pilots an option in the middle. The airfield was officially commissioned on January 20, 1954, by which time it was already in regular use. It served as a safety net. Planes refueled here. Distressed aircraft put down here. It was not a destination so much as a chance to keep flying the most direct line between places that did not want to detour five hundred kilometers east.

In the 1970s, the Brazilian military looked at Cachimbo and saw not just a refueling stop but a piece of ground large enough and remote enough for weapons work. On March 7, 1983, the Campo de Testes do Cachimbo was created, subordinated to the Brazilian General Command for Aerospace Technology. The name changed twice. On January 17, 1995, it became Campo de Provas Brigadeiro-do-Ar Haroldo Coimbra Velloso, honoring the commander who built the infrastructure, and on July 30, 1997, it settled into its current name: Campo de Provas Brigadeiro Velloso. The complex spans four municipalities - Altamira, Itaituba, Jacareacanga, and Novo Progresso - and its 653-kilometer perimeter runs through some of the most remote ground in Brazil. The renovated airfield was renamed Cachimbo Airport on August 18, 1979.

The apron handles up to twenty small aircraft with full support and maintenance facilities - a scale suited to the testing complex it serves rather than to passenger traffic. No military units are permanently based here. No scheduled flights operate from the field. Cachimbo is a military airport, operated by the Brazilian Air Force but not classified as an Air Force Base, a distinction that matters in procurement and command structure more than in practice. It is for exclusive military use. A unit of the Amazon Surveillance System, SIVAM, also operates out of Cachimbo, providing part of the radar coverage that lets Brazilian authorities track movement across a border region where drug trafficking and illegal mining are constant concerns. From the air, the runway looks like what it is: a paved scar in green canopy that stretches to the horizon.

On September 29, 2006, Cachimbo became the emergency field it was designed to be. A brand-new Embraer Legacy 600 executive jet, flown by two American pilots who were ferrying it to its Florida-based owner, struck a Gol Transportes Aereos Boeing 737-800 in level flight at 37,000 feet over the jungle below. The winglet of the Legacy sliced off about half of the 737's left wing. The 737, operating as Flight 1907, lost controllability and broke up in the air. All 154 people on board were killed, scattered across the forest floor in the Serra do Cachimbo. The Legacy, badly damaged but still flyable, found Cachimbo on a visual approach and landed. The seven occupants walked away uninjured. The collision became the deadliest aviation accident in Brazilian history until that point, and it raised hard questions about air traffic control, transponders, and the gaps in radar coverage over the Amazon that SIVAM was supposed to close.

Cachimbo Airport is about fifteen kilometers from BR-163, the federal highway that runs from Cuiaba in Mato Grosso north to Santarem on the Amazon River. The highway matters less to the airport than the absence of other access matters. BR-163 brings soybean trucks from the Cerrado toward their export terminals, but Cachimbo itself is not on the highway. To reach the airport you turn off and follow a restricted-access road. The isolation is the asset. Weapons testing, aircraft maintenance, and the overflight monitoring that SIVAM performs all benefit from being far from everywhere else. The forest around the perimeter is largely intact because people with other business have been asked, firmly, to go elsewhere. Most of them have.