ATT's pension fund is only about 75% funded and that 75% includes a large amount of a special class of ATT preferred stock (esssentially an IOU). This special class of prreferred stock was created just to address a serious underfunding problem (at least on paper) in 2012. If ATT were to default on all this debt and its pension obligations, the impact on the financial system and the US economy would be enormous. It's stunning to think that the US government stood by and watched as these fools built this bomb, especially after the events of 2008. If you want a scary look into what else the ATT geniuses have done, read the followind old article from Forbes: https://www.forbes.com/sites/edwardsiedle/2012/10/25/att-proposes-massive-dump-of-company-stock-into-pension/#642b7c0d5e8d.
OP is @WlwlNTx-cua . Liked the points that he made on the matter