TWA,
Whether or not AA actually reaffirmed TWA's debt to its former TLV employees during their merger/acquisition of the company through a written instrument (and therefore made an affirmative assumption of such) is immaterial. There exists significant legal precedent requiring AA to assume TWA's debt to its former TLV employees regardless of whether they themselves actually acknowledge such simply by virtue of the merger/acquisition.
Even the article you copied and pasted clearly states that upon review of Israeli Labor Law, AA themselves believe they are likely responsible for this debt. Hence, without delving extensively into semantics, for the purpose of this specific debt, AA likely assumed it from TWA by virtue of it's merger/acquisition of TWA according to Israeli labor law.