# Boeing Starliner

The Boeing Starliner (or CST-100) is a spacecraft designed to transport crew to and from the International Space Station (ISS) and other low-Earth-orbit destinations. Developed by Boeing under NASA's Commercial Crew Program (CCP), it consists of a reusable crew capsule and an expendable service module.
Slightly larger than the Apollo command module or SpaceX Crew Dragon, but smaller than the Orion capsule, the Starliner can accommodate a crew of up to seven, though NASA plans to fly no more than four. It can remain docked to the ISS for up to seven months and is launched on an Atlas V N22 rocket from Cape Canaveral Space Launch Complex 41 in Florida.
In 2014, NASA awarded Boeing a US$4.2 billion fixed-price contract to develop and operate Starliner, while SpaceX received $2.6 billion to develop and operate Crew Dragon. By February 2025, Boeing's effort had exceeded its budget by at least $2 billion.
Originally planned to be operational in 2017, Starliner has been repeatedly delayed by problems in management and engineering. The first uncrewed Orbital Flight Test in December 2019 was deemed a partial failure, leading to a second Orbital Flight Test in May 2022. During the Crew Flight Test, launched in June 2024, the Starliner's thrusters malfunctioned on approach to the ISS and NASA concluded that it was too risky to return its astronauts to Earth aboard the spacecraft, which landed uncrewed in September 2024.

## Background

As the Space Shuttle program drew to a close, NASA sought to foster the development of new spaceflight capabilities. Departing from the traditional model of government-owned and operated spacecraft, NASA proposed a revolutionary approach: companies would own and operate spacecraft, while NASA would act as a customer, purchasing flights as needed. To incentivize innovation, NASA offered funding to support the development of these new vehicles. However, unlike previous cost-plus contracts, these new contracts would be fixed-price, placing the financial risk of cost overruns on the companies themselves.
Boeing has an extensive history of developing vehicles for space exploration, having built the first stage (S-IC) of the Saturn V rockets, assembling the Lunar Roving Vehicles, and serving as the prime contractor for the US Orbital Segment of the ISS since 1993. With its proven track record and deep expertise, Boeing was seen as well-positioned to compete for the commercial spaceflight contracts.
In 2010, Boeing unveiled its entry into NASA's Commercial Crew Program competition: the CST-100. The company received initial funding of $18 million in the first round of the Commercial Crew Development (CCDev 1) program to support Starliner's development. Additionally, United Launch Alliance, a joint venture between Boeing and Lockheed Martin, secured $6.7 million to develop the Emergency Detection System to allow its Atlas V rocket to be human-rated to launch Starliner. At the time, Boeing expressed optimism that the Starliner could be operational as early as 2015, contingent upon timely approvals and funding.
In October 2011, NASA announced that the Orbiter Processing Facility-3 at Kennedy Space Center would be leased to Boeing for manufacture and test of Starliner, through a partnership with Space Florida.
Over the next three years, NASA would hold three more rounds of development funding, awarding Boeing $92.3 million under CCDev 2 in 2011, $460 million under the Commercial Crew integrated Capability (CCiCap) program in 2012, and $9.9 million under the Certification Products Contract (CPC) in 2013.
NASA was expected to announce its selection for the lucrative Commercial Crew Transportation Capability (CCtCap) contract in September 2014. Boeing had lobbied NASA for a sole-source contract, arguing that it needed the program's full budget for the successful development of Starliner. Within NASA, there was considerable support for this approach, with many decision-makers expressing confidence in Boeing's capabilities and safety record. In fact, NASA officials had even drafted a justification for selecting Boeing as the sole provider.
While William H. Gerstenmaier, NASA's human exploration lead, had considered the Starliner proposal as stronger, he was hesitant to award a sole-source contract. The multi-year Commercial Crew Program had been designed to foster competition and redundancy, and Gerstenmaier believed that selecting just one company would undermine these goals. Through his efforts, he successfully convinced NASA to delay the CCtCap announcement and secure additional funding to support two competing efforts.
On September 16, 2014, NASA announced that both Boeing and SpaceX would be awarded CCtCap contracts to develop crewed spacecraft. Boeing received a US$4.2 billion to complete and certify the Starliner, while SpaceX received a US$2.6 billion to complete and certify Crew Dragon. To receive the full contract amount, each company would need to successfully complete an abort test, an uncrewed orbital flight test, a crewed orbital flight test, and six crewed missions to the ISS. However, NASA would not need to pay for any failed tests and was only required to purchase two crewed missions to the ISS from each company. Following the initial guaranteed missions, the companies would compete for launch contracts on an ongoing basis.
In November 2015, NASA announced that it had dropped Boeing from consideration in the separate multibillion-dollar Commercial Resupply Services competition to fly cargo to the International Space Station.

## Development

The name CST-100 was first used when the capsule was unveiled to the public in June 2010. The acronym "CST" stands for Crew Space Transportation, while the number "100" represents to the Kármán line, the unofficial boundary of space located at an altitude of 100 kilometers (62 mi) above Earth. The design draws upon Boeing's experience with NASA's Apollo, Space Shuttle, and ISS programs, as well as the Orbital Express project.
The spacecraft consists of a reusable capsule and an expendable service module and is designed for missions to low Earth orbit. The capsule accommodates seven passengers, or a mix of crew and cargo. For NASA missions to the ISS it will carry four passengers and a small amount of cargo. The Starliner capsule uses a weldless, spun-formed structure and is reusable up to ten times with a six-month turnaround time. Boeing plans to alternate between two reusable crew modules for all planned Starliner missions. Each flight uses a new service module, which provides propulsion and power-generation capacity for the spacecraft. Starliner features wireless Internet and tablet technology for crew interfaces.
Starliner uses the NASA Docking System. Boeing modified the Starliner design prior to OFT-2, adding a hinged re-entry cover below its expendable nosecone for additional protection of the docking port during atmospheric entry. This was tested on the OFT-2 mission. By contrast, the reusable SpaceX Dragon 2 nosecone is hinged and protects its docking port during both launch and reentry.
The capsule uses the Boeing Lightweight Ablator for its re-entry heat shield.
Solar cells provided by Boeing subsidiary Spectrolab are installed onto the aft face of the service module, providing 2.9 kW of electricity.
In addition to the capsule and service module, a 5.8 ft (1.78 m) structure called an aeroskirt is integrated into the launch vehicle adapter of Atlas V. The aeroskirt provides aerodynamic stability and dampens the shock waves that come from the front of the rocket.
The spacecraft's propulsion system is produced by Aerojet Rocketdyne and consists of 64 engines:
* 12 × 100 lbf (440 N) MR-104J RCS (reaction control system) thrusters on the capsule, using hydrazine monopropellant and reserved for orienting the capsule during atmospheric re-entry
* 52 on the service module using monomethylhydrazine and nitrogen tetroxide bipropellant:
** 28 × 85 lbf (380 N) RCS thrusters on the service module for attitude control during the majority of the flight
** 20 × 1,500 lbf (6,700 N) OMAC (orbital maneuvering and attitude control) thrusters for altering orbits
** 4 × 40,000 lbf (180,000 N) RS-88 engines for launch escape capability in the event of an abort
The RCS and OMAC thrusters on the service module are grouped into four "doghouses" equally spaced around the perimeter of the service module, each containing five OMAC thrusters (three aft-facing and two forward-facing), and seven RCS thrusters: two aft-facing, two forward-facing, and one each in the radial and two tangential directions. The latter three are in a plane which is very close to the spacecraft's center of mass.
To translate the spacecraft, thrusters are used in balanced pairs so that the center of force goes through the spacecraft's center of mass. To rotate the spacecraft, thrusters are used in unbalanced pairs so there is no net force and the net torque is centered within the spacecraft. The RCS thrusters are used for rotation (attitude control) and very fine docking maneuvers, while the OMAC thrusters are used for significant orbital adjustments. The RCS thrusters are also used to compensate for slight imbalances in the OMAC thrusters.
Boeing designed the capsule to make ground landings instead of a splashdown, a first for a crewed capsule mission launched from the United States. After reentering the atmosphere, three parachutes will be deployed, slowing the capsule to approximately 4 miles per hour (350 ft/min; 1.8 m/s). Before reaching the ground, six airbags will deploy to cushion the landing. There are four primary landing locations, including two sites inside the White Sands Missile Range in New Mexico, the Willcox Playa in Arizona and the Dugway Proving Ground in Utah. Edwards Air Force Base in California serves as a contingency landing location. All of the landing sites are in the Western United States, allowing the service module to be jettisoned for a destructive reentry over the Pacific Ocean. Boeing says that between all five landing sites, there will be around 450 landing opportunities each year.
Following the award of the Commercial Crew Transportation Capability (CCtCap) contract in 2014, NASA assigned a team of four experienced astronauts, Bob Behnken, Eric Boe, Doug Hurley and Sunita Williams, to serve as consultants to engineers at both Boeing and SpaceX. These astronauts were also slated to be the test pilots on the inaugural missions. Hurley recounted a stark contrast in the working relationships between the astronauts and the engineers at the two companies. While the SpaceX engineers were receptive to feedback, enthusiastic about collaborating, and attentive to suggestions, Hurley found the Boeing engineers to be indifferent, arrogant, and overconfident. He also said the Boeing team failed to inform the astronauts about the propellant leak that occurred during the Pad Abort Test. Ultimately, Hurley told the chief of the astronaut office that he would not fly on Starliner. Hurley and Behnken would later go on to command the Crew Dragon's historic Demo-2 mission, the first crewed flight of the spacecraft. Williams would fly into space on the Boeing Crew Flight Test, but would return to Earth on a Crew Dragon, after thrusters malfunctioned on the Starliner.
Despite being initially awarded significantly more funding, Boeing has faced substantial budget overruns for the Starliner program, exceeding $2 billion as of February 2025.
In November 2019, NASA's Office of Inspector General released a report revealing that a change to Boeing's contract had occurred in 2016, stating: "For Boeing's third through sixth crewed missions, we found that NASA agreed to pay an additional $287.2 million above Boeing's fixed prices to mitigate a perceived 18-month gap in ISS flights anticipated in 2019 and to ensure the contractor continued as a second commercial crew provider", and NASA and Boeing committed to six missions instead of the last four being optional.
In August 2024, after the setbacks experienced during the Crew Flight Test, NASA Administrator Bill Nelson stated that Boeing CEO Kelly Ortberg committed to continuing the Starliner program. However, financial analysts expressed skepticism that Boeing would continue to invest in a money-losing program and in October The Wall Street Journal reported that Boeing was exploring a sale of some of its space division programs, including Starliner. As of January 2025 NASA and Boeing have not announced plans for the next flight.

## Testing

Various validation tests began on test articles in 2011 and continued on actual spacecraft starting in 2019.

### Abort and drop tests

In September 2011, Boeing announced the completion of a set of ground drop tests to validate the design of the airbag cushioning system. The airbags are located underneath the heat shield of the Starliner, which is designed to be separated from the capsule while under parachute descent at about 5,000 ft (1,500 m) altitude. The airbags, manufactured by ILC Dover, are deployed by filling with a mixture of compressed nitrogen and oxygen gas, not with the pyro-explosive mixture sometimes used in automotive airbags. The tests were carried out in the Mojave Desert of southeast California, at ground speeds between 10 and 30 mph (16 and 48 km/h) in order to simulate crosswind conditions at the time of landing. Bigelow Aerospace built the mobile test rig and conducted the tests.
In April 2012, Boeing dropped a mock-up of its Starliner over the Nevada desert at the Delamar Dry Lake, Nevada, successfully testing the craft's three main landing parachutes from 11,200 ft (3,400 m).
Boeing reported in May 2016 that its test schedule would slip by eight months in order to reduce the mass of the spacecraft, address aerodynamics issues anticipated during launch and ascent on the Atlas V rocket, and meet new NASA-imposed software requirements. The Orbital Flight Test was scheduled for spring 2019. The booster for this Orbital Flight Test, an Atlas V N22 rocket, was assembled at United Launch Alliance's (ULA) facility at Decatur, Alabama by the end of 2017. The first crewed flight (Boe-CFT) was scheduled for summer 2019, pending test results from Boe-OFT. It was planned to last 14 days and carry one NASA astronaut and one Boeing test pilot to the ISS. On April 5, 2018, NASA announced that the first planned two-person flight, originally slated for November 2018, was likely to occur in 2019 or 2020.
A serious incident occurred during a hot-fire test in June 2018. A design flaw in the propellant system left four of eight valves open, leading to the release of over 4,000 pounds (1,800 kg) of toxic monomethylhydrazine propellant, resulting in a fireball that engulfed the equipment. The incident was reportedly exacerbated by animosity with the propulsion system subcontractor, Aerojet Rocketdyne, who Boeing refused to pay for design changes. While it informed NASA of the incident, Boeing attempted to keep the incident quiet, even withholding information from the astronauts involved in the project.
In October 2018, the first unpiloted orbital mission was delayed to April 2019, and the first crew launch was rescheduled to August 2019. In March 2019, Reuters reported that these test flights had been delayed by at least three months, and in April 2019 Boeing announced that the unpiloted orbital mission was scheduled for August 2019.
In May 2019, all major hot-fire testing, including simulations of low-altitude abort-thruster testing, was completed using a full up-to-service module test article that was "flight-like," meaning that the service module test rig used in the hot-fire testing included fuel and helium tanks, reaction control system, orbital maneuvering, and attitude-control thrusters, launch abort engines and all necessary fuel lines and avionics that will be used for crewed missions. This cleared the way for the pad abort test and the subsequent uncrewed and crewed flights.
A pad abort test took place on November 4, 2019. The capsule accelerated away from its pad, but then one of the three parachutes failed to deploy, and the capsule landed with only two parachutes. Landing was, however, deemed safe, and the test a success. Boeing did not expect the malfunction of one parachute to affect the Starliner development schedule.

### First orbital flight test (uncrewed)

The uncrewed Boeing Orbital Flight Test (OFT) launched on December 20, 2019, bearing an Anthropomorphic Test Device nicknamed "Rosie the Rocketeer" and clothed in Boeing's blue IVA spacesuit as well as a Plush toy of Jedediah Kerman from Kerbal Space Program. It landed two days later, having nearly ended in catastrophic failure. The mission was ultimately declared a partial failure.
After launch, the spacecraft captured a "mission elapsed time" from its Atlas V launch vehicle that was 11 hours off. Consequently, when the spacecraft separated from the rocket, instead of briefly firing its reaction control thrusters to enter orbit, its computers commanded them to fire for far longer, consuming so much fuel that the spacecraft no longer had enough to dock with the ISS. As the capsule was prepared for re-entry, another software error was discovered; it could have caused a catastrophic collision between the service module and crew capsule.
The spacecraft landed at White Sands Missile Range, New Mexico, two days after launch. After its landing, NASA astronaut Sunita Williams named the spacecraft Calypso after the research vessel RV Calypso used by oceanographic researcher Jacques Cousteau.
After the mission, Boeing vice president John Mulholland acknowledged that the company had not conducted integrated end-to-end tests for the entire mission, but had instead performed tests of smaller segments. This approach contributed to the software errors that led to the near-catastrophic failures during the flight test. Mulholland insisted that Boeing cut no corners, and that end-to-end tests were not omitted to save money. NASA was also faulted for not pressing Boeing to conduct an end-to-end test.
The subsequent NASA–Boeing investigation into the flight made scores of recommendations for Boeing and NASA. Boeing declared these to be proprietary, so the only ones publicly known are the ones that officials deliberately disclosed. In 2020, company officials said they were addressing 80 of the recommendations.

### Second orbital flight test (uncrewed)

Because the first OFT did not achieve its objectives, Boeing officials said on April 6, 2020 that the Starliner crew capsule would fly a second uncrewed demonstration mission, Boeing Orbital Flight Test 2 (OFT-2), before flying astronauts. NASA said that it had accepted a recommendation from Boeing to fly a second unpiloted mission. The Washington Post reported that the second orbital flight test, with much the same objectives as the first, was expected to launch from Cape Canaveral "sometime in October or November 2020". Boeing said that it would fund the unplanned crew capsule test flight "at no cost to the taxpayer". Boeing told investors earlier in 2020 that it was taking a US$410 million charge against its earnings to cover the expected costs of a second unpiloted test flight. Boeing officials said on August 25, 2020 that they set the stage for the first Starliner demonstration mission with astronauts in mid-2021. Boeing modified the design of the Starliner docking system prior to OFT-2 to add a re-entry cover for additional protection during the capsule's fiery descent through the atmosphere. This re-entry cover is hinged, like the SpaceX design. Teams also installed the OFT-2 spacecraft's propellant heater, thermal-protection tiles, and the airbags used to cushion the capsule's landing. The crew module for the OFT-2 mission began acceptance testing in August 2020, which is designed to validate the spacecraft's systems before it is mated with its service module, according to NASA. On November 10, 2020, NASA's Commercial Crew Program manager Steve Stich said that the second orbital flight test would be delayed until first quarter 2021 due to software issues. The uncrewed test continued to slip, with the OFT-2 uncrewed test flight being scheduled for March 2021 and the crewed flight targeted for a launch the following summer. The launch date of OFT-2 moved again with the earliest estimated launch date set for August 2021.
During the August 2021 launch window some issues were detected with 13 propulsion-system valves in the spacecraft prior to launch. The spacecraft had already been mated to its launch rocket, United Launch Alliance's (ULA) Atlas V, and taken to the launchpad. Attempts to fix the problem while on the launchpad failed, and the rocket was returned to the ULA's VIF (Vertical Integration Facility). Attempts to fix the problem at the VIF also failed, and Boeing decided to return the spacecraft to the factory, thus cancelling the launch at that launch window. There was a commercial dispute between Boeing and Aerojet Rocketdyne over responsibility for fixing the problem. The valves had been corroded by intrusion of moisture, which interacted with the propellant, but the source of the moisture was not apparent. By late September 2021, Boeing had not determined the root cause of the problem, and the flight was delayed indefinitely. Through October 2021, NASA and Boeing continued to make progress and were "working toward launch opportunities in the first half of 2022", In December 2021, Boeing decided to replace the entire service module and anticipated OFT-2 to occur in May 2022.
The OFT-2 mission launched on May 19, 2022. It again carried Rosie the Rocketeer test dummy suited in the blue Boeing inflight spacesuit. Two Orbital Maneuvering and Attitude Control (OMAC) thrusters failed during the orbital insertion burn, but the spacecraft was able to compensate using the remaining OMAC thrusters with the addition of the Reaction Control System (RCS) thrusters. A couple of RCS thrusters used to maneuver Starliner also failed during docking due to low chamber pressure. Some thermal systems used to cool the spacecraft showed extra cold temperatures, requiring engineers to manage it during the docking.
On May 22, 2022, the capsule docked with the International Space Station. On May 25, 2022, the capsule returned from space and landed successfully. During reentry one of the navigation systems dropped communication with the GPS satellites, but Steve Stich, program manager for NASA's Commercial Crew Program, said this is not unexpected during reentry.

### Third orbital flight test (crewed)

The Starliner's crewed flight test was originally planned as the capsule's final test before entering regular service. This test would have involved launching two astronauts into orbit, docking with the International Space Station for approximately a week, and conducting additional tests while ground crews reviewed data from the launch and docking. Following a review and approval of this data, the capsule would have undocked and returned to Earth for a landing in the American Southwest about eight days later. However, the capsule's thrusters malfunctioned as Starliner docked with the ISS, and despite months of testing, NASA felt it was not able to understand why the thrusters malfunctioned and decided that it was too risky to return its astronauts to Earth aboard Starliner, so it returned uncrewed.
Originally planned for 2017, the launch faced numerous delays, including issues with the parachute harness and flammable tape on wiring. These delays pushed the launch back to mid-2024.
A launch attempt on May 6, 2024, was scrubbed due to an oxygen valve problem on the rocket. Subsequently, a helium leak in the service module further delayed the mission. Another attempt on June 1 was scrubbed due to a ground computer hardware fault. Starliner successfully launched on June 5 at 14:52 UTC (10:52 am EDT).
Once in orbit and on approach to the ISS during this flight test, both the automated systems and astronauts taking manual control during the docking sequence were instructed to repeatedly fire the RCS thrusters. This stress testing revealed performance degradation in the thrusters, leading the spacecraft software to consider five of them damaged and unusable, and five separate helium leaks were detected in the service module. The five failed thrusters were all aft-facing, resulting in a loss of six degrees of freedom attitude control until four of them were restored. The astronauts were able to safely dock the capsule to the ISS.
A joint NASA–Boeing team spent weeks trying to understand what caused the thrusters to malfunction, conducting ground tests at the White Sands Missile Range in New Mexico on the Aerojet Rocketdyne thruster that was planned to be used on a future Starliner mission, and working with the astronauts to replicate their testing in space. During these tests, the ground team was able to replicate the thrust degradation, and tied it back to a Teflon seal had been deformed by a buildup of heat. However, when these tests were conducted on the Starliner in orbit, the problem was not replicated.
Ultimately, NASA felt it was not able to understand why the thrusters malfunctioned and decided that it was too risky to return its astronauts to Earth aboard Starliner, which returned uncrewed. Boeing, for its part, has expressed confidence in Starliner and believes there is flight rationale for returning the spacecraft to Earth with the astronauts aboard.
Starliner landed safely in the White Sands Missile Range in New Mexico on 7 September at 04:01:35 UTC (6 September, 11:01:35 pm MDT, local time at the landing site), about six hours after it undocked from the ISS. Starliner experienced two new technical problems unrelated to its earlier issues during the reentry. There was a brief glitch in Starliner's navigation system, and one of the 12 thrusters used to orient the capsule during atmospheric re-entry failed to ignite.
NASA says that it will review all mission-related data to inform what additional actions are required to meet its certification requirements. NASA Administrator Bill Nelson has stated that Boeing CEO Kelly Ortberg has committed to continuing the Starliner program despite the setback.
Boeing officials were scheduled to participate in a post-landing news conference, but they abruptly canceled at the last minute without providing a reason. After NASA decided to end the Starliner test flight without a crew on board, the company refused to answer questions from journalists, instead opting to release only brief statements.

## Commercial use

Under the CCP, Boeing owns and operates the Starliner capsules, allowing the company to offer non-CCP commercial flights if they do not interfere with NASA missions. While SpaceX has secured private commercial flights, Boeing has yet to do so.
The CCP agreement permits Boeing to sell seats for space tourists on ISS flights. While initially proposed, the extended length of typical ISS missions makes this unlikely.
In October 2021, Blue Origin, Boeing, and Sierra Nevada Corporation announced plans for a commercial space station called Orbital Reef. This "mixed-use business park" could be serviced by both Starliner and Sierra Nevada's Dream Chaser spacecraft.

## Launch vehicle

Starliner was designed to be compatible with multiple launch vehicles, including the Atlas V, Delta IV, Falcon 9, and Vulcan Centaur.
For the three completed test flights and up to six further missions, Starliner is expected to fly atop the Atlas V. However, United Launch Alliance, the operator of the Atlas V, ceased production of the rocket in 2024 after producing vehicles for all remaining contracted launches. The vehicles have been allocated to customers, including the six needed for the remaining Starliner flights.
The Starliner faces an uncertain future after that. Delta IV is retired and no more are available, the Falcon 9 is owned by crewed launch competitor SpaceX, and the Vulcan Centaur has not yet been human-rated, testing Boeing would have to pay for.

### Configuration

For Starliner launches, ULA uses the Atlas N22 configuration. All other Atlas V launches use a payload fairing and the single-engine version of the Centaur upper stage. N22 is configured with no payload fairing, two solid rocket boosters (SRBs), and a Dual Engine Centaur second stage. Starliner is the only crewed payload for Atlas V.
While most Atlas V launches since 2021 have used the newer Northrop Grumman GEM63 SRBs, these boosters are not rated for human spaceflight. Therefore, crewed missions employ the older Aerojet Rocketdyne AJ-60A SRBs.
Although the Dual Engine Centaur had not been used since 2000 after the introduction of the more powerful Atlas V, it was brought back into service for Starliner missions. Two engines allow the rocket to fly a gentler and flatter trajectory to minimize the G-forces experienced by the astronauts and ensures the capsule can abort at any time, returning the crew to Earth in case of a problem.

## Launch profile

After passing through the stages of max q, SRB jettison, booster separation, Centaur ignition, nosecone and aeroskirt jettison, it releases the Starliner spacecraft at stage separation, nearly 15 minutes after lift-off on a 112 mi × 45 mi-high (181 km × 72 km) suborbital trajectory, just below the orbital velocity needed to enter a stable orbit around Earth. After separating from the Dual Engine Centaur, the Starliner's own thrusters, mounted on its service module, boost the spacecraft into orbit to continue its journey to the International Space Station.
The suborbital trajectory is unusual for a satellite launch, but it is similar to the technique used by the Space Shuttle and Space Launch System. It ensures that, if the spacecraft fails to make the orbital insertion burn, it will re-enter the atmosphere in a controlled way. The Starliner's orbit insertion burn begins about 31 minutes into the mission and lasts 45 seconds.

## List of spacecraft

As of January 2020, Boeing planned to have three Boeing Starliner capsules in service to fulfill the needs of the Commercial Crew Program with each capsule expected to be capable of being reused up to ten times with a six-month refurbishment time. On August 25, 2020, Boeing announced it would alternate between just two capsules for all planned Starliner missions instead of three.
| S/N | Name | Type | Status | Flights | Flight time | Total flight time | Notes |
| S1 | None | Prototype | Retired | 1 | 1m 19s (PAT) | 1m 19s | Prototype used only for pad abort test. |
| S2 | TBA | Crew | Active | 1 | 5d 23h 54m (OFT-2) | 5d 23h 54m | Completed the OFT-2 flight. |
| S3 | Calypso | Crew | Active | 2 | 2d 1h 22m (OFT) 93d 13h 9m (CFT) | 95d 14h 31m | Named after Jacques Cousteau's ship RV Calypso. First Starliner to orbit during OFT, first to carry crew to space during CFT. |

## List of flights

List includes only completed or currently manifested missions. Dates are listed in UTC, and for future events, they are the earliest possible opportunities (also known as NET dates) and may change.
| Mission and Patch | Capsule | Launch date | Landing date | Remarks | Crew | Outcome |
| Pad Abort Test (patch) | S1 | November 4, 2019 | November 4, 2019 | Simulating an escape from a failing rocket, Starliner's RS-88 engines lifted the capsule from a pad at White Sands. Only two of three parachutes opened, but was declared a success. | — | Success |
| Orbital Flight Test (patch) | S3.1 Calypso | December 19, 2019 | December 22, 2019 | First uncrewed orbital flight test. Orbited but failed to rendezvous with ISS. Landed successfully. | — | Partial failure |
| Orbital Flight Test 2 (patch) | S2.1 | May 19, 2022 | May 25, 2022 | Second uncrewed orbital flight test. Experienced OMAC and RCS thruster malfunctions, but successfully docked to ISS. | — | Success |
| Crew Flight Test (patch) | S3.2 Calypso | June 5, 2024 | September 7, 2024 | Crewed flight test to ISS. Landed uncrewed due to malfunctioning RCS thrusters. | Barry Wilmore Sunita Williams | Partial failure |
| Starliner-1 | S2.2 | TBD | TBD | | Scott Tingle Michael Fincke Joshua Kutryk Kimiya Yui | Planned |
| Starliner-2 | TBD | TBD | TBD | | TBA | Planned |
| Starliner-3 | TBD | TBD | TBD | | TBA | Planned |
NASA has only placed firm orders for three Starliner flights once the capsule is certified for operational use. Under the terms of its contract with Boeing it has the option to purchase up to six operational flights, Starliner-1 through Starliner-6. However, it is unclear if it will be possible to operate that many missions before the scheduled retirement of the ISS in 2030.

## Technology partners

* Aerojet Rocketdyne, reaction control system and retrorockets
* Airborne Systems, parachutes
* Bigelow Aerospace, elements of crew capsule
* Collins Aerospace, life support systems
* David Clark Company, spacesuits
* ILC Dover, airbags
* Samsung, mobile communications technology
* Spincraft, crew module pressure shell spin-form work