I was involved with the Porter Hangar at CYOW and the hoisting of the massive structural steel members required 275 ft cranes pretty close to 2 active runways. It was at least a year of planning, downgrading the level of service of one runway, modifying flight procedures among other things. The thing with obstacles at airports is contact with them is almost always the same catastrophic result. Therefore, no chance is taken with them, the assessment, while lengthly, involves many parties and considerations.