STB puts Union Pacific-Norfolk Southern merger review on hold, asks for more supplemental filings

The U.S. Surface Transportation Board (STB) paused key parts of its review of Union Pacific and Norfolk Southern’s proposed combination, ordering the railroads to provide supplemental information by July 27 before the merits of the deal move forward.

In a May 28 decision, the STB said it accepted for consideration the companies’ revised major merger application filed April 30, after the Board previously rejected their initial filing as incomplete in January 2026. The Board characterized the current step as a narrow “completeness” determination, not a ruling on whether the transaction is in the public interest. It also held proceedings in abeyance, including the transaction’s environmental review, while it evaluates the supplemental submissions.

The STB said it still needs additional detail in several areas under its “modernized” rail-merger rules, including enhanced competition, access for 2-to-1 and 3-to-2 shippers, diversion analysis tied to public benefits, and the service assurance plan. It also listed topics such as market share projections, downstream merger impacts, gateway and car-supply issues, passenger rail, and workpapers. In the same decision, the agency said discovery would not be affected, but it did not immediately set the remainder of the procedural schedule.

Union Pacific and Norfolk Southern said in response that they would continue working with the STB to provide the requested information. The companies told investors they believe the merger would strengthen competition and reduce costs for customers, and they framed the revised application as data-driven and focused on seamless integration. STB’s action shifts the timetable by delaying when formal review steps begin, even though the revised filing has been accepted for consideration.

The pause carried immediate market impact. Reuters reported that on May 28, shares of Union Pacific fell 4.2% and Norfolk Southern dropped 5.4% after the STB said it had paused the application review while seeking more information, with the environmental review also on hold.

The stalling also reflects the STB’s broader approach to railroad consolidation, which it says now emphasizes competitive enhancement and potential downstream effects on shortline railroads, ports, employees, communities, and other stakeholders. In a customer notification dated May 28, BNSF said the STB treated the revised application as technically complete but was “disappointed” that key aspects remained unclear, and it warned that acceptance does not equal approval.

Still, several uncertainties remain. While the STB enumerated categories of supplemental information it wants, it did not publish in its short notice what, specifically, will be missing or how those additions might change the analysis. The Board also indicated it would establish an appropriate procedural schedule later, leaving stakeholders without firm dates for subsequent filings.

What to watch next is the content and timing of the supplemental submission due July 27, and whether the STB then issues a procedural schedule for evidentiary proceedings. The companies have previously indicated an expectation that the transaction could be completed in mid-2027, but the STB’s order shows regulators can pause the process even after accepting an application as complete.