SHIELD's Helicarriers were the ultimate symbol of the spy agency's power in the MCU but Shuri of Wakanda had a different opinion and name for them.
Marvel just gave SHIELD's Helicarriers a different, but appropriate, new nickname. The greatest symbol of SHIELD's power as the world's foremost global spy agency, the Helicarrier made its on-screen debut in 2012's The Avengers. SHIELD's mobile base of operations, under the command of Director Nick Fury (Samuel L. Jackson), was an aircraft carrier that could fly using four gigantic turbines. After The Avengers, Tony Stark (Robert Downey Jr.) upgraded the Helicarriers with Stark repulsor technology, which would allow the flying fortress to remain in the air indefinitely.
The Helicarrier seen in The Avengers was No. 64 and it withstood an attack by Loki's (Tom Hiddleston) mind-controlled SHIELD agents, which included Hawkeye (Jeremy Renner). No. 64 also had a cage built to imprison the Hulk (Mark Ruffal0) that Loki was briefly incarcerated in, and the Helicarrier also withstood a rampage from within by the green goliath. In 2014's Captain America: The Winter Soldier, Hydra (which was part of SHIELD since its inception) launched Project Insight: three brand new Helicarriers linked via satellite that were housed in the Triskelion in Washington, D.C. Project Insight's Helicarriers were designed to pursue thousands of targets deemed a threat to Hydra and eliminate them, but they were eventually destroyed by Captain America (Chris Evans), Falcon (Anthony Mackie), Black Widow (Scarlett Johansson), and Nick Fury. Helicarrier No. 64 reappeared in 2015's Avengers: Age of Ultron and evacuated the people of Sokovia during the Avengers' battle with Ultron (James Spader).
The Helicarriers are impressive and intimidating technological marvels but they are also problematic, hence the accurate nickname given to them by Shuri (Leticia Wright). In the new book The Wakanda Files: A Technological Exploration of the Avengers and Beyond, which was commissioned in-universe by Shuri, the Wakandan Princess gives her own evaluation of SHIELD's hallmark weapon. But Shuri has a more withering view of SHIELD's mighty Helicarriers and she dubbed them "giant airborne Titanics". Of course, the RMS Titanic was the biggest and most famous luxury liner of its era; renowned for its epic size and scale, the Titanic is infamous for sinking after hitting an iceberg on its maiden voyage across the North Atlantic to America, as depicted in the blockbuster 1997 Oscar-winning film Titanic directed by James Cameron. The RMS Titanic was lost on April 10, 1912, and it remains a lasting symbol of mankind's hubris.
Shuri has good reasons to be skeptical of SHIELD's Helicarriers and to compare them to the RMS Titanic. The Helicarriers are also a symbol of SHIELD/Hydra's power and hubris, and the evil world-conquering organization intended to use Project Insight's Helicarriers to dominate and terrorize the globe. Project Insight's triad of Helicarriers also went down in flames thanks to Captain America and his friends, and they were essentially three Titanics themselves.
However, to be fair to SHIELD and their Helicarriers, the heroic flying fortress that Nick Fury controlled never went down in battle. Helicarrier No. 64 survived The Avengers intact and without it, the Avengers couldn't have saved the citizens of Sokovia in Age of Ultron. Hydra may have ruined the Helicarriers just as they defiled SHIELD's reputation in the MCU, but Fury, at least, maintained one Helicarrier away from Hydra's clutches and he used it for the purpose SHIELD originally intended it for.
In the alternate timeline of Marvel's Agents of SHIELD season 7, Helicarrier No. 64 reappears in the series finale under the command of the new Director of SHIELD, Alphonso "Mack" Mackenzie (Henry Simmons). In Agents of SHIELD's version of the MCU, the Helicarrier has been restored to its original status as SHIELD's ultimate weapon and a symbol of peace and security, and it remains the farthest thing from the "giant airborne Titanic" that Shuri believed the Helicarrier to be.