Sorry to take OP's thread off track, but Widgets's typical FlyerTalk absolution of the airline bugged me, so I went back to the LiveATC feed to confirm, and indeed at about 6:06 in the feed the pilot clearly announces to ATC that, despite being cleared in to land on 4R, "company just ordered us to divert to Boston". It's not even like Delta was particularly badly affected by Sunday's chaos--Terminals 1 and 8 were shut down, but 2 and 4 seemed unaffected other than the general ground stop that was in place for a while.

I'm giving Delta a try on the theory that their operations are better than AA's, and I suppose I'm just unlucky because in addition to Sunday's debacle there's been minor problems leading to delays with two other flights as well. I'll hope that my experiences revert to the mean before too long, and see if Delta does anything other than the e-mail they sent Sunday night blaming the diversion on "security concerns".