The Gulfstream IV (or G-IV or GIV) and derivatives are a family of twinjet aircraft, mainly for private or business use.

They were designed and built by Gulfstream Aerospace, a General Dynamics company based in Savannah, Georgia, United States, from 1985 until 2018.

[2] In 2001, Gulfstream began work on an improved version of the GIV-SP, originally designated GIV-X.

Speed, noise levels, emissions, fuel economy, range, and cargo capacity were also markedly improved over the earlier model.

[9] The Gulfstream IV wing has a weaker, more swept outboard shock resulting in a lower cruise drag.

[10] In addition to the wing redesign, the Gulfstream IV also became the first business jet to have an entire glass cockpit.

[11] The G400 has a large cabin, long range of 4,350 nautical miles (8,060 km) and the same comfort and design that characterize the G series.

[9] The National Oceanic and Atmospheric Administration (NOAA) operates a GIV-SP (N49RF) modified to fly scientists and crew members at 45,000 feet around tropical cyclones.

The aircraft was modified to drop instruments called "dropsondes" to measure windspeed, barometric pressure, humidity, and temperature as they fall to the surface of the ocean.

The GIV-SP is suited for this mission since it is fast, and can fly long distances with ample cabin space for the crew and instruments.

[12] In 2009, the NOAA GIV-SP was further modified by the addition of a side-scanning Doppler weather radar to the rear fuselage.

Compared to the Gulfstream IV, its fuselage is 12 inches longer and the main entry door relocated aft.

The Rolls-Royce Tay 611 engines are replaced by 611-8Cs with FADEC, redesigned thrust reversers, nacelles and pylons which increases range and payload, coupled with aerodynamic improvements.