OPSGROUP has published a briefing note asking a question that business aviation, charter and compliance teams have increasingly had to answer for themselves: what actually changes if an aircraft sits below the 45,500 kg maximum take-off weight line? The post, titled "Below 45.5 Tonnes: What Difference Does It Make?", follows the group's earlier treatment of the same subject, published under the headline "The 45.5T Elephant in the Security Room", and it lands in a narrow but consequential corner of aviation regulation, where a single number on a type certificate or weight schedule can…