Bombardier Global series

The Global series are similar in appearance, but have more and smaller cabin windows and different style cockpit windows. Also there is an APU exhaust in the right side of the tail cone and an air intake in the root of the dorsal fin.

Canadair Regional Jet 700

The CRJ700 looks more like the Global above than a Gulfstream, and also has has many small cabin windows and different style cockpit windows. Typical is the APU exhaust at the end of the tail cone.

Grumman G.159 Gulfstream I

This may seem a strange entrance here at first, but leave out the prop engines, tail and wings and it is easy to mix up the G-I and G‑II. The wings are placed more aft on the G‑II than on the G-I though, and have a larger wing-body fairing on the jet version.

After Gulftream invented the IIB the company Aviation Partners designed its own winglets for the Gulfstream II. Compared to the winglets of the IIB the transition between the wings and the winglets is curved.

The Gulfstream IITT is the only Gulfstream with tip tanks, so it is easy to recognise. For the rest it is the same as the standard G-II.

Starting with the Gulfstream III the Gulfstream jets have a more streamlined cockpit with four curved windows, and standard winglets. It has five cabin windows like the G-II, so the cockpit windows are the way to distinguish it from G-II variants.

The Gulfstream III is known by the US forces as the C-20A, C-20B, C-20C, C-20D and C‑20E.

This is a stretched G-III with wider diameter Rolls Royce Tay engines instead of the Rolls Royce Spey engines. Their nacelles have external fairings for the thrust reverser mechanism. The G-IV has six cabin windows on each side, one more than on earlier models. The G-IVSP is an enhanced G-IV, but it cannot be distinguished from the G-IV externally. When Gulfstream introduced new marke­ting designations the Gulfstream IVSP became the G400. The G300 has a smaller range and less standard options, but is otherwise the same. Both are externally not different from the G-IV and G‑IVSP. Note that the thrust reversers and their fairings are normally metallic, but sometimes they are painted to make the aircraft look like a G450!

Military versions of the G-IV are designated C‑20F, C‑20G and C-20H by USAF, US Army and US Navy, Tp102 and S102 by the Swedish forces and U-4 in Japan.

The G450 is a slightly stretched G400 with the nose (actually cockpit) of the G550. So it is longer, but this is only visible when you see a G-IV and G450 side-by-side, by the larger distance between the cabin door and the cockpit windows. The G450 can especially be distinguished from the other G-IV versions by the engine nacelles, with a different type of thrust reversers: compared to the G-IV it has no fairings on the outside which has clearly visible fairings for the reversers. Note that the normally metallic thrust reversers and fairings of the G-IV can be painted to make the aircraft look like a G450! See photo above.

Unfortunately Gulfstream pulls the same trick with the G450 as with the G400: there is a G350, which looks the same, but it has a smaller range and less standard options. There is one external feature which can tell you that you have a G350 in front of you: the absence of the EVS camera below the nose, which is standard on the G450 but optional on the G350.

The marketing name G400 is used for a second time on a three metre shorter version of the G500. It has same design characteristics as the G500 and G600: it has its new cockpit windows, winglets without a curve under an angle of 45 degrees compared to the wing, lower landing gear when on the ground, etc. The key recognition point are the five large oval cabin windows on each side.

This is a lengthened G-IV, but the G-V still has six windows on each side. Is identified by the MD‑80-like tail, the more streamlined engine nacelles without external fairings for the thrust reversers and the large space between the cabin door and the first cabin window.

C-37A is the American military designation of the G-V. The Israeli special mission variant is locally named Nachshon Shavit.

This was the shortest version of the based on the G650, until the launch of the even shorter G400. Like the G600 it has most often seven cabin windows on each side, but sometimes only six. To recognise it from the G600 you have to look at the distance between the main cabin door and the first window: this is larger at the G600 than the G500. For the rest it resembles its larger sibling: it has its new cockpit windows, non-curved winglets under 45 degrees compared to the wing, lower landing gear when on the ground, etc. However, the engine nacelles are different. Unlike the G650, G700 and G800, the G500 has thrust reversers at the very end of the nacelle. This is the same on the G600.

The G550 was originally going to be called G-VSP and is an improved version of the G-V. It is the last Gulfstream type based on the fuselage of the Gulfstream II (and even the Gulfstream I). It has seven windows on each side, and therefore easy to distinguish from the G-V. The G500 is a G550 with a smaller range and less standard options. Like the G350/450, the G500 and 550 are externally the same, except that the EVS below the nose is optional on the G500.
Only a few G500s were sold. Therefore the marketing name was later reused on the new aircraft based on the G650.

The US forces designate the VIP version of the G550 as C-37B. 

The Gulfstream G550 proves to be a popular platform for special mission aircraft, as it is in used as an airborne early warning and control aircraft with the air forces of Israel, Singapore, Italy and USA. In Israel they are named Nahshon-Eitam or Oron (depending on application), while Italy designates them as E-550A. The US Navy has a missile range support aircraft, named NC-37B. The EA-37B (originally designated EC-37B) of the USAF has the same external shape.
All feature large bulbs in the nose, tailcone, the side of the fuselage (it has no cabin windows) and on top of the vertical stabiliser. 

The G600 fits between the smaller G500 and larger G650. You can recognise it by its seven cabin windows, although the smaller G500 often has seven cabin windows as well. To recognise the G600 from the G500 you have to look at the distance between the main cabin door and the first window: this is larger on the G600 than the G500, about the width of two windows. For the rest it looks like its siblings. Another way to distinguish the G600 from the G650 (and G700 and G800) is the fact that the G600 has its thrust reversers at the very end of the nacelle. They are further forward on the G650 (see photo at G500).

The G650 was the start of a new family. It barely looks like the original; only the large oval cabin windows are a clear reminiscent of the earlier versions. For the rest it is a new aircraft:

• a larger diameter fuselage
• cockpit windows with a "swept" trailing edge of the aft windows
• a new, high aspect ratio wing
• winglets at an angle of 45 degrees with respect to the wings, not curved at the top
• shorter main gear legs when on the ground
• horizontal stabilisers with some dihedral

The G650 has eight cabin windows, one more than the G600 and one or two more than the G500. Additionally, the thrust reversers are slightly before the end of the nacelle, unlike on the G500 and G600.

The G650ER is the extended range version, externally not different from the standard G650.

To be better able to compete head-on with the Bombardier Global 7500 the Gulfstream G650 was stretched to create the G700. The longer fuselage means room for more cabin windows, ten on each side. Another clear recognition point compared to the G500/G600/G650 are the curved winglets, especially near the top. They are still canted with regard to the wing tips.

The intended successor to the G650ER has the same fuselage, but then mated to the wings and tail of the G700. The G800 also has the same engines as the G700. From a recognition viewpoint this means that the eight cabin windows are no means to distinguish the G650 and G800. However, the slightly curved (tops of the) winglets are what to look for.