The first teaser trailer for Spider-Man: Far From Home featured a fake suit to fend off Avengers: Endgame spoilers. Marvel Studios and Sony Pictures Entertainment had to be creative in marketing the latest Jon Watts-directed flick due to the events of Avengers: Infinity War where Peter Parker (Tom Holland) died. While it's an open secret that those who were affected by Thanos' (Josh Brolin) snap would eventually return, the studios had to stick with the narrative. And with only a couple of months in-between Far From Home and Endgame, they had to be careful with what they included in the former's first trailer.
Released back in January, shortly after Marvel Studios rolled out the first look at Endgame, Far From Home's teaser trailer skirted around the events of Infinity War. The clip featured Peter back in New York, and preparing for his European trip. Its opening scene, however, had a major difference from what ended up in the movie, as Peter wore his Spider-Man: Homecoming costume, instead of the Iron Spider suit.
This was an intended creative decision as explained by ILM’s Far From Home visual effects supervisor Julian Foddy. Since the movie's first teaser trailer came out before Endgame hit theaters, Marvel didn't want to reveal that the nano-tech costume survived the events of Infinity War and its sequel. “They didn’t want to reveal that Spider-Man survived Infinity War and his possession of the Iron Spider suit on Earth would have given that game away,” he explained to Befores and Afters in a recent interview.
In subsequent trailers and TV spot released after Endgame's roll out, Peter was seen wearing the correct suit. At this point, fans already knew how he survived and came back to Earth. He even wore the same costume during the massive battle against Thanos and his minions in Avengers 4's final action set piece. However, since that particular bit of the scene where Peter and Aunt May (Marisa Tomei) faced the crowds was never the focal point of succeeding marketing footage, the swap in the hero's suit was more subtly done.
This is not an uncommon practice, especially with Marvel Studios movies. They typically use fake and/or edited scenes in their marketing to preserve the secrecy of the narrative. Spider-Man was famously removed from an early Captain America: Civil War trailer prior to his official debut, and Captain America (Chris Evans) wore a different suit in Avengers: Endgame special look to misdirect theories. Small changes like this in Spider-Man: Far From Home should be okay since they don't drastically change what fans can expect from the movie itself. But if heavily manipulated trailers turn out to be selling something entirely different from what end up in the big screen, then that would be a problem.
Source: Befores and Afters