Why was I woken up last night by aircraft noise?

Like most commercial airports in the US, St. Louis Lambert International (STL) operates 24 hours per day 365 days per year. There is no nighttime curfew . However, the City of St. Louis, in coordination with the FAA, airport users and community representatives, has developed preferred nighttime aircraft procedures that help mitigate aircraft noise over residential areas. Depending on winds and weather conditions, these procedures are designed to align aircraft with the runways in the safest and most efficient manner possible.