Shares of General Motors (GM:US) and Ford Motor (F:US), two of the largest names in the American automotive industry, saw their shares decline on Thursday amid mounting investor concerns regarding potential labor strikes and the subsequent ramifications for these automakers.

General Motors saw its shares nosedive by as much as 5.5%, while Ford faced a decline of up to 4.6%, causing ripples of concern across the financial market. The situation garnered attention as both companies have been grappling with the possibility of labor strikes initiated by the United Auto Workers (UAW) union.

Earlier this week, Bloomberg reported that the UAW had tabled new contract demands that, if implemented, could result in a staggering increase of over $80 billion in labor costs for each of the automotive giants. 

The UAW's proposed contract demands include substantial wage hikes, improved benefits packages, and enhanced job security provisions for workers. 

United Parcel Service (UPS:US) recently announced a deal with the workers union. Accordingly, UPS drivers are set to receive an average annual pay and benefits package of $170,000 as part of a new five-year contract agreement. 

The agreement marked the conclusion of a protracted negotiation period between UPS and the Teamsters Union, which aimed to avert a potential strike and secure improved terms for the 340,000 union employees.

UPS stock price was whipsawing for weeks on deal reports, with GM and F stocks now going through the same scenario.

Congressmen Ro Khanna and Bill Keating were lately trading GM shares. The former was selling the stock in mid-July, with shares trading about 15% lower roughly 3 weeks later.