On the airline side, Delta, United, American, and Air France all route you through their respective hubs with solid hard products. Delta's One Suite gives you a closing door and 1-2-1 configuration — genuinely private, with Tumi kits and generally the most consistent service on the transatlantic legs via Amsterdam or Paris connections. United's Polaris pod is also 1-2-1 lie-flat with Saks Fifth Avenue bedding and Polaris lounge access at hubs like Newark or Chicago, a strong option if your itinerary naturally routes that way. American's Flagship Business gives you a lie-flat suite, Casper bedding, and Flagship Lounge access through hubs like Philadelphia or Chicago. Air France's business cabin is lie-flat 1-2-1 as well, and if your connection runs through Paris, you get their well-regarded French cuisine and, depending on cabin class and lounge access tier, entry to La Première lounge — a nice perk even for business passengers routing through CDG. For Detroit to Glasgow business class, the connection city often matters as much as the airline, since layover length and lounge access can shape the whole travel day.