 theorem\] Let ${\mathcal{K}}$ be an abstract elementary class with no maximal models of cardinality $\mu^+$ which satisfies the joint embedding and amalgamation properties. Suppose $\mu\geq\operatorname{LS}({\mathcal{K}})$. If ${\mathcal{K}}$ is $\mu$- and $\mu^+$-superstable and satisfies $\mu^+$-symmetry, then for any increasing sequence $\langle M_i\in{\mathcal{K}}_{\geq\mu^{+}}\mid i<\theta<(\sup\|M_i\|)^+\rangle$ of $\mu^+$-saturated models, ${\bigcup}_{i<\theta}M_i$ is $\mu^+$-saturated.  