LaTeX (amsmath): Left aligned equtations in {equation} or {align} container

Question

I have the following problem

\usepackage[fleqn]{amsmath}

\begin{equation}
    \begin{split}
        \min Y\\
        \textrm{s.t.}
    \end{split}
\end{equation}
\begin{align}
    a+b=145641574\\
    c+d<e
\end{align}

creates the following output:

So far so good. The formulas are essentially left-aligned. The numbering is right-aligned. But within the formulas, splits or line breaks result in right alignment. These should also be left-aligned.

Thanks in advance and have a nice weekend!