AMEMB Brussels message to Americans there: shelter in place, avoid public transportation.
http://1.usa.gov/1RwUkVq
Yeah, that is only sustainable for hours at most.
Not counting the immigrant issue, this attack reverberates throughout the West due to the transportation targets hit. The disruption at other airports due heightened security and the temporary closure of BRU makes this a much higher payoff target than Stade de France or Bataclan.
I would be interested in hearing from anyone traveling by air domestically or internationally in the next 24-48 hours as to changes in security.