By September 1937, all eight Gladiator squadrons had achieved operational status and had formed the spearhead of London's air defences.[16] Difficulties with introducing the type had been experienced. Although the Gladiator was typically well liked by pilots, the accident rate encountered during operational training for the type were so numerous that a small replacement batch of 28 Gladiator Mk IIs was hurriedly produced.[15] Most accidents were caused by pilots being caught out by the fighter’s increased wing loading and many aviators had little experience in landing aircraft with such a wide flap area.[15] The aircraft had a tendency to stall more abruptly, frequently dropping a wing while doing so. The Gladiator proved even easier to enter a flat spin with and great skill was needed to recover.[17][15]