I don't know where else to post an edit suggestion:
"Urd only asks himself how many were allowed to die, and if the missile attack was enough to end his companions, how lucky for the attackers."
^ I'm fairly certain that Urd was referring to his fellow vampires, NOT the "attackers". He was stating that if any of his vampire comrades had died from the blast, they should be considered fortunate for having been killed so easily (and thus released from the curse of being a vampire).
Hi, these article talk pages, the Forum or Discussions are good! Vampires who want to be released from their 'curse' can easily do it, finding a foe to 'lose' to is straightforward. With this, suggests Urd does not consider it lucky for vampires to die, they can die at any time.
Another factor is sure Urd could have changed his mind, but he saw the vampire state of being as superior to humans. He also wondered if Saito was looking for an excuse to die, but Urd himself did not appear to really have such notions himself.
As Ly Luc illustrated when he said he is going to kill whoever ordered the missile strike on their aircraft, and Urd asking about Lest Karr and Krul's status (would just assume they were happy and freed from the curse if he did consider it that way) it lends Urd's statement to being interpreted in a certain manner.
Considering these points, Urd's "If that was enough to do it, (if the missiles were enough to kill the vampires, including his fellow progenitors who like him were capable of avoiding the missiles) how lucky for them." (moot point: how lucky they were allowed to die to escape the curse/how lucky the attackers managed to kill the progenitors, since they are coming for you otherwise - Urd's faint smile could apply to both, but not if he does not see dying as a relief). The latter point is read as whoever ordered the strike has angered a bee's nest/progenitor members, if it were enough to kill the progenitors, lucky for the attackers otherwise as Ly Luc shows, whoever ordered it is in deep trouble.
Then again maybe it is a sign of a change in demeanor and Urd now does consider the vampires who fell as lucky for escaping the curse of being vampires... This might be a we will have to wait to see if Urd does feel this way towards dying, and how he feels about the state of being a vampire in later chapters and what he says to Rigr (the suspected attacker) if he finds him again.
In any case until that time if and when it comes, feel free to write the page how you like. All that can be done is simply document the facts and so something like "Urd observes the falling aircraft and asks how many were allowed to die, if that were enough to do it how lucky for them". Facts stated, how the reader interprets that moment at this point in the story is up to them.