The thread that jeffh747
linked to is a great resource.
The extension built in the 1960s is roughly from current gates G6/G7 upward. From inside, it’s clearly noticeable that the building gets wider and the floor in the far end of the concourse is higher up, as evidenced by the ramp near G8.
When the 21st Street Terminal originally opened in 1959 with the numbered concourses, it was roughly Eastern on concourses 5 and 6 (later D and C), Braniff on concourse 5, Pan Am and foreign carriers on concourse 4 (E), National and Northeast on concourse 3 (F), and the rest of the domestic carriers on concourse 2 (G). Delta moved to concourse 1 (now H) when it opened in 1961 and has been there ever since. No other airline at MIA has operated from the same concourse for anywhere near as long as Delta’s 58 years at H.
When American first started flying to MIA in 1979, they used gates at G. As their operation grew in the mid 1980s, they started using some gates on H. Once they bought Eastern’s Latin American network, AA moved out of concourse G and H to concourses D and E, eventually expanding to concourse C, then B, then A, until everything was merged together into the present linear terminal.
Since G’s most recent extension was built in the 1960s and the most recent remodel was in the 1970s, it has a lot of unusual attributes. It’s the only two story concourse, the only concourse that cannot handle international arrivals, and the only concourse without an underground hydrant fueling system. A lot of the gates have staircases to the ground level since they were constructed when propliners were still popular. Bahamasair uses gate G6 as a ground load gate and has passengers walk across the tarmac to the airplane when they send their ATR. Also, virtually every gate from G8 up thru G19 is a widebody gate that can accommodate aircraft like the DC-10 and L-1011 that were popular in the 1970s. Many of the gates still have stop bars for classic airliners like the 707 and DC-8. Gates G16 and G19 can even accommodate 747s.
Through the 1980s and 1990s, G continued to serve a menagerie of domestic carriers, including Continental, Northwest, TWA, Tower Air, United, and ValuJet (later AirTran). Air Canada also used gates on G.
Continental was with Eastern at D In the 1980s but moved to G by the 1990s. United moved to F in the early 1990s when they bought Pan Am’s Latin American routes and made a half hearted attempt at a hub.
Tower Air shut down in 2000 and TWA merged with AA in 2001. Air Canada moved to concourse J when it opened in 2005. Continental moved to newly vacated gates in H around the same time. In the 1990s, Bahamasair used to use gates at the far end of H that were permanently closed to accommodate a dual taxiway when J opened, so they must’ve moved to G in the early 2000s. Northwest merged with Delta in 2008 and moved to Delta’s gates in H.
By the end of the 2000s, G was largely a ghost town, with the only carriers being Alaska, AirTran, Bahamasair, Gulfstream, Sun Country, and charter flights to Cuba operated by an ever changing assortment of airlines, including Allegiant Air, Sky King, and Vision. Alaska, AirTran, and Gulfstream all pulled out in favor of FLL.
Nowadays the current tenants are Bahamasair, Frontier, Sun Country, Sunwing, and United.
When Continental and United announced their merger in 2010, there wasn’t room at H and J to consolidate their combined operations, so they moved to the current split concourse arrangement where some flights are out of G and some are out of H. United tries to put as many flights are they can on H with its more modern facilities, but during peak times they have up to four aircraft overnighting at G. United currently uses gates G9, G11, G15 (former Northwest gates) and occasionally G16 or G19.
Frontier has been in G since they started flying to MIA in 2014. MIA is now their newest base and their typical gates are G8, G10, G12, G14, and sometimes G16. I call it the morning zoo because of all the animal tails lined up at 6 AM.
Bahamasair typically uses G6 or G8, and sometimes G4. These are the same gates Sun Country tends to use for their seasonal service during the winter.
Sunwing is a relatively new airline at MIA with seasonal winter service. Their flights to/from Canadian airports with US CBP preclearance tend to use G8, G10, or G12. The flights without preclearance use F.
In the summer there are also charter flights to the Caribbean (typically the Dominican Republic) operated by carriers like Eastern 3.0 (formerly Dynamic), Swift Air, and World Atlantic.
Gate G1 is now closed but featured a lower level waiting area and 4 or 5 parking positions for small propeller aircraft like the Beechcraft 1900, but it hasn’t been used since Gulfstream (now Silver) pulled out of MIA. They used to have a sizable operation with service to various cities in Florida and the Bahamas. The 1900s used to park in pairs parallel to the terminal where gates G3 and G5 were. Nowadays G3 is just a parking lot and the G1 holdroom is abandoned and blocked off.
Gates G5 and G7 have no jet bridges and are used as “remote” parking only, though Swift Air will occasionally have a ferry flight without passengers leave from one of those spots. On the Google Maps satellite image, you can still see the lead in lines for the props on G5, and the ones on G6 which are still used. G7 featured the airport’s last remaining “mini me” jet bridge, which fell into disrepair by the start of the 2010s and was removed.
Gate G2 was permanently closed not too long ago for some sort of terminal expansion between G and H. I have no idea what it’s for but it seems to be office space.
Gates G14, G16, and G19 can accommodate larger widebodies and were regularly used as additional “remote” parking (typically LATAM 767s spending the day at MIA before heading back to South America at night) until Frontier built up their operation in November. Gate G14 also has the longest jet bridge at MIA.
Taxiway P runs abeam gates G14, G16, and G19. When an A380 uses this taxiway to get between runway 9 and concourse J, the service road which runs behind these gates is blocked off by the aviation department because the wingspan is wider than the taxiway and the outboard edges of the wings pass over the service road, posing a threat to traffic.
Gate G17 existed but was evidently eliminated at some point during the 1980s. If you compare the first two photos you can see that the jet bridges on the west side have moved and the bridges no longer correspond to the stairwells.
Here are some overviews of G:
The most current plan for concourse G is to demolish it and use the area for remote parking. Eventually E and F are to be demolished as well and the area occupied by E, F, and G will be home to two new super concourses. The recent Frontier expansion might put a damper on the demolition plans for G since there’s nowhere else they can fit unless they don’t mind being spread across two or three concourses like Air Florida was back in the day, or like how United is now.