What do NOTAMs typically inform controllers about?

NOTAMs, or Notices to Airmen, primarily serve to communicate important information to pilots and air traffic controllers regarding significant operational changes or hazards that may affect flight operations. This can include changes to airspace usage, runway conditions, navigational aids, or other relevant details that could impact safety.

The information contained in NOTAMs is crucial for ensuring that all parties involved in aviation are aware of current conditions and can make informed decisions during flight planning and operations. Therefore, the correct answer emphasizes the importance of these significant updates which are essential for maintaining safety in the aviation environment.

Other choices generally represent types of information not covered by NOTAMs. Future flight schedules are handled by airlines and flight operations rather than safety notices. Weather reports are typically communicated through different channels, such as METARs or TAFs. Routine maintenance updates, while important, do not generally rise to the level of urgency or significance that requires a NOTAM. Thus, option B accurately captures the essential role that NOTAMs play in aviation safety.